Well, I've done it:  I've now played both the 360 and the PS3.  Last weekend, my best friend saved up enough the premium system, along with The Elder Scrolls 4: Oblivion and Gears of War. (We also got Perfect Dark Zero free with the system.)

It was great that the system came with component calbes; we hooked it up to my HDTV and surround sound, and my excitement was arguably greater than when I was hooking up the PS3. (maybe not.  I was pretty damn excited for the PS3.)
Here's my impression of the games that we played for 360 so far:

 
The Elder Scrolls IV: Oblivion:  I won't lie, Oblivion is an impressive game, but to be honest it's my least favorite so far.  This is probably because I usually dislike RPGs, but that's not to say that I don't like anything about it.  I do admire a lot of elements, particularly the amazing amount of depth in the character creation and custimization.  I'm a sucker for that stuff.  It's an enormous game with enormous environments, and the graphics are downright purdy.

Perfect Dark Zero:  Awesome, awesome, awesome.  At first, I was a bit put off by the cartoony artstyle for an M rated game, as well as the lame opening level (who wants to shoot little bugs in a next-gen FPS?).  However, I kept playing, and the game grew on me very quickly.  The weapons that I've used so far have a great sense of uniqueness and kick to them, and the sense of style in the game rocks.  Just watching Joanna Dark put a silencer on a pistol has me giddy.

Gears of War:  This is the game that everyone's judging the 360 by, and it doesn't dissapoint.  The gameplay is intense and surprisingly original, even though it borrows elements from past shooters (and does them about 10x better.).  I love the graphics, it has a perfectly fitting, gritty, almost horror-themed style.  The meat of the game is the shooting, and luckily firefights are intense and are even designed to be slightly different each time you play.  Chainsawing a locust in half is the best melee since the feral punch from Far Cry.  Overall, it's an exteremely impressive game.  There were a few annoying elements to the gameplay (I have to revive my teammates every five seconds but they can't revive me?) and I was annoyed by the blatant lack of story, but besides that it's great.

So, overall I love the 360.  I still remember back in E3 '04 when I was sure that I'd die before I bought one, and now I'm truly jealous.  I want one.
I wanted to avoid this topic, but it seems pretty inevitable when sizing up the system.  How does it compare to the PS3?  At the moment, my inner fanboy wants to talk about how much more powerful the PS3 is, but to be honest I've had more fun with the 360 so far (with Resistance being the exception), and I don't see a significant difference in graphics.  Having said that, I'm sure the PS3 will start truly offering the thrills later this year (just like the 360 did).  Regardless, I'm just glad that now I can experience the best of both systems.