I can safely say after finishing it in less than two minutes I have no desire to buy the full version.  The main three things that bother me ...  
 
1.  Sonic goes through animations really slowly and the controls generally feels sluggish. 
2.  The camera needs to be pulled back so you can see a little more. 
3.  The music, while in theory is the right move, doesn't sound quite right. 
 
Now I don't want this to turn into a hate thread, and I actually was looking forward to this release.  Let's keep this for people that have actually played it and have something meaningful to contribute please.

Sonic

People don't like the new Sonic game.
 
I'm shocked.

Just finished playing the trial. It was okay I guess but man, fuck Sonic. I really hope nobody is foolish enough to buy this. Sonic must die.

I've never really liked Sonic so i can't really give an unbiased opinion, however, I do love the music from the games and can tell you that from what I heard, it's kind of disappointing. 

It made me feel like a dog. It looked right at first glance but everything about it smelled wrong. The music felt like I was having a nightmare about Sonic. The movement felt weird like you can slow walk up walls, but what really got me or rather scared me was the freaky way Sonic's finger moves on the main menu. It looked like i was being scolded by The Grudge.

The presentation music etc is all good its just the actually part you play just feels iffy like its been said Sonic moves in a really slugguish way and when first starting to run it seems like sonic is dragging a canon ball behind him, maybe it was just this level but the game just seems slower than previous 2d sonic games even the rush games felt faster than this. What did it for me though was after playing the trial then looking at the price 1200 points seems way to much 800 maybe is a little more on the money seeing as it well be in episodes.

Is the music more Hideki Naganuma? That's literally the only part of Sonic I've been interested in since the music for Lava Reef in Sonic 3. 
 
  

Shortest demo I've ever played. Aside from that, nothing really stood out for me.

Sonic looked as though he was trying to run under water it was very sluggish. Also there was  no momentum as soon as you let go of the stick he stop's dead in his tracks. I haven't played the old sonic's in a couple of months but I don't remember just stopping like that. I would just pick up Sonic's ultimate genesis collection as you can probably find it for the same price as Sonic 4 and get a lot more games.

" People don't like the new Sonic game.  I'm shocked. "

I agree that the control of Sonic doesn't feel right. He's too slow. The visuals and music are pretty good though and I did like the enemy lock-on feature quite a bit. I can't see myself purchasing this game and believe that it would be a better deal to just buy the first two Sonic games for $10 and get much more enjoyment out of playing those. 

everyone here is crazy
at first i wasn't happy about the homing attack, (being only a fan of sonic 1 and 2)
but the demo was awesome, i'll be picking it up tomm and loving it

" People don't like the new Sonic game.  I'm shocked. "

I enjoying hearing the Sega intro. Thats pretty much all I enjoyed.

Did not enjoy it at all. Among many things, I hated the music most.

" Sonic "

Sonic fans are the worst fucking kind of people.
 
They don't even fucking know what they want at this point. It's just "FUCK YOU, SEGA! MAKE A GAME I LIKE!! NO, YOU'RE DOING IT WRONG! WHAT'S THAT, A NEW 2D SONIC GAME LIKE I SAID? FUCK YOU, THIS SHIT SUCKS! MORE FURRY PENIS IN MY MOUTH PLEASE, HORATIO!"

It was too short.  Other than that it felt like Sonic.

" @Ventilaator said:

" People don't like the new Sonic game.  I'm shocked. "

  

"

I think Jeff said it best: "you can't always go back home". i played the demo once and then deleted it. from it i cam way with one major thought, i feel bad for sega. this was a lose/lose situation from the start. when they try to take sonic in a new direction, it comes off as sloppy and poor and is followed by people yelling that they should just give the fans what they want: a sonic game that plays just like the old ones. then they decided to try and go back to their roots with this game and the game just oozes with a "look, you wanted old sonic, so we'll give you old sonic" and it feels like that. so now they will hear people just telling them that they messed up the old sonic. end result, sonic is done. sega needs to just put out one last collectors pack of the old sonics in hd for those who want them and then just wash their hands of sonic b/c there is no way they can revive what they had with him in the 90's and this is the best example of that

Since I have a Genesis plugged into my TV right now (and all the Sonic games) I can assure you that Sonic 4 plays just like every other game in the series. Sonic has always been very slow to start running, and running into walls and enemies has always stopped him dead in his tracks, making the games sometimes incredibly frustrating. Still, the level design in Sonic 4 is quirky, the music is oddly appropriate for a Genesis/Mega Drive game, and the new homing attack does add a little bit of depth to the platforming. In short, its Sonic. I kind of wish they had taken more inventive liberties with the title like they did in the Advance Series (Sonic Advance 3 is particularly inventive with its buddy system) but this is the first Sonic in years that's a fun, playable video game. Even if it does play it too safe. 
 
Low standards? Maybe, but its still a bright light for the series when compared to all that has come before it.

This thread is funny. This game is just like Sonic 1-3. Sonic always started out slow and got a lot faster. Go back and play Sonic on the Genesis. He moves in the exact same way. Sonic fans are truly impossible to please. They asked for a decade for Sega to make a 2D Sonic just like the old ones. So Sega did and now people realize what many others have known for years - Sonic wasn't that great of a game. It certainly doesn't hold up nearly as well as Mario. Everything people are complaining about besides the music are things that have always been in Sonic. If you didn't want a Sonic exactly like the old ones then why did you ask for it?

Sluggish controls, overly zoomed camera, mind-numbingly boring level design and the ugliest graphics in a Sonic side-scroller ever.

I can't help but wonder if the people at Sega actually believe Sonic will ever be good again, or if they're consciously milking the fuck out of the fanbase with terrible games.

" @Ventilaator said:

" People don't like the new Sonic game.  I'm shocked. "

"

I think the issue with the music might be that they made it so very close to the classic Sonic themes the fact it's a tiny bit off creates a kind of auditory uncanny valley.

" It was too short.  Other than that it felt like Sonic. "

Slightly disappointed by it, but to be honest I haven't really given it a fair shot yet since I've only played the demo so take my opinion with a grain of salt. It seems like it could be the best Sonic game to come out in years, but I still don't feel it stacks up to the original games in a number of ways. 
 

1. I don't like the art style. It feels strange to say it but the original games were more aesthetically pleasing to me.
2. Gameplay feels sluggish. I hate the way Sonic just immediately stops dead the minute you stop moving. I do however, like the inclusion of the homing attack, it's a great way to keep momentum when you're just flung up vertically into the air.
3. Level design feels a little strange. Some of the jump pads and swing ropes seem to be placed in really strange positions and kill momentum, I'm all for gimmicks which prevent the whole "hold right to win" bullshit but there are better ways of doing it.

Pretty much agree with the OP.  I liked the idea of making the music sound like the classic 8-bit tunes, but something seems to have gone badly wrong.  The animation looks bad, the graphics look bad and the momentum is completely off, resulting in the gameplay looking, sounding and feeling absolutely nothing like Sonic.

Even the Advance/Rush games handled more like classic Sonic than this does, I was honestly shocked at just how bad the game is.  Doesn't help that after the first stage the level design rapidly deteriorates into the typical speed booster/holding right affair. 
 
I originally said at 400 points this would have been an instant buy regardless of quality.. I wouldn't have even downloaded the trial.  All I can say now is that I'm very glad it wasn't 400, because that still would have been a waste of money.

" @SethPhotopoulos said:

" It was too short.  Other than that it felt like Sonic. "

It did feel like Sonic, but I don't really like Sonic that much, and the thought of it being episodic or costing me that much is exhausting. It seems OK. I was excited to try it, and less excited to actually play it. "

Just picked up the demo. I've played it many times. To try to like it. And it just isn't happening. 
 
The controls seem a bit odd, I feel like spin dashing is slower than using the burst from a homing attack in the direction you're going in, you're far too vulnerable because of the camera and the fact that the level is just one giant trap, as opposed to a platform to go from one place to another and...I just generally don't enjoy it.  
 
It just feels like something is off. I can't pin it down.