I heard that the online system does a pretty good job at matching you up with similarly skilled players so it maybe not be a complete blowout every time.  I am a little scared of this game since I am more of a casual rts player and don't have these games down to a science like the better players do.

You'll at least enjoy the campaign.  Based on the GB live stream last night, it seems like it starts pretty slow.

Just know up front you are going to lose. Probably not every game, but you'll need to be able to look at a loss not as a failure but as a learning experience, look at what you did wrong and correct it next time.  But if you can accept that you will lose some times I think you can have a fun time with it.

I never even touched sc1 and my last rts experience was in 2000 playing c&c red alert. 
 
And in SC2 i´m doing pretty good. I won 3 out of 5 games( not being vain, just surprised). Just google for some SC2 Tutorials and start slow.  
 
http://starcraft2strategies.org/  
 
Right know i´m  figuring out the best Build Order for my Gamestyle. Terran are quite easy for beginners i would say.

I think anyone can be really good at Starcraft, its just that in order to do that it takes a ton of work, commitment and suffering.  Same with any RTS really.

As far as the campaign, is it more user friendly than the first? I could never even beat the Terran campaign in SC1, so is there more room to advance without getting super frustrated? And I hear they have unlock trees for singleplayer, how do those work? I'm getting awfully aggravated at no early reviews being allowed, and I'm fed up with $60 gambles.

The level of entrance needed for multiplayer is sky high outside practice matches while the campaign is incredibly generic both in story and for the genre (by genre I mean rts games that came out a decade ago).

" As far as the campaign, is it more user friendly than the first? I could never even beat the Terran campaign in SC1, so is there more room to advance without getting super frustrated? And I hear they have unlock trees for singleplayer, how do those work? I'm getting awfully aggravated at no early reviews being allowed, and I'm fed up with $60 gambles. "

I'm a couple of hours in. Trust me the game is ultra polished, the campaign is great, the achievements are great (finally good gameplay based achievements), the battle net implementation is great, there is lots of tutorial stuff if you're new and then there are challenge modes and stuff that I haven't checked out yet. I don't know if you're only interesting in playing it online but the game as a single player experience is ultra polished, too. This will get 90s all over the board.

 Terran are quite easy for beginners i would say. "

I'm not the greatest at the multiplayer aspect of the game, but I do find it thoroughly enjoyable, and the campaign looks very interesting.  So, I'd say it was worth a look.