For the record, I didn't play a lot of 2, haven't touched HD Remix (due to it being released one day before SFIV was for PAL PS3 users (Thursday then Friday respectively)), nor have I ever played 3. I have however played a lot of Alpha 3 Max on my PSP, lots of fun.
So I went into SF IV relatively noobish. But thankfully I'm not doing too badly now. My current records is Played: 161, won: 65, which is roughly 40%. My battle points for what it's worth (not a lot IMO) is currently 635, although it has been 700+.
The online seems to be much better than most fighting games, I have even been playing against Spanish players who usually have the worst connections on the planet. I had already planned beforehand to install the game on my PS3, so your experience may vary.
As far as players go I have been playing Sagat exclusively, I want to get him to a level I'm happy with before I start fresh on some secondary characters. I think he's great, love his range. I've been playing against mainly Ken users for better or worse, I've got used to his playstyle now, a lot of Ryus, the odd Sakura player, quite a few Akuma players ranging from average to pretty good, I find Gouken players harder to be honest. I've very little experience against Blanka players, the few I have played were all better than me by far.
I unlocked and completed the game with all characters on the first day I got the game but I've resisted to urge to use Seth, it just wouldn't seem right.
I'm always looking for challenges so I can improve myself, my PSN is also FLStyle, see you there.