This has been pretty much my most awaited game of the year, and I just got it last night (finally got to play it this afternoon)
For anyone who hasn't heard about it, CC was made by Dan Paladin and Tom Fulp, from Newgrounds.com, the same team that made Alien Hominid (flash/gamecube/ps2/xbox live arcade). Castle Crashers is a 3D game in the vein of Golden Axe or Double Dragon (side scroller with 2D sprites, where you move away from/towards the screen as well as forwards through mostly linear levels).
The story is simple, 4 princesses were kidnapped and it's up to you (and maybe some friends) to rescue them. The gameplay is really retro feeling, hold right and mash buttons until you get to a spot where you gotta defeat all the baddies that spawned, but the wide selection of enemies help keep it fresh.
There's also a slight RPG element to it, like a Gauntlet game, but you pick which stats increase each level.
So far I've found ~ 8 total weapons, and unlocked one new knight (they're color coded and their colors represent their magic)

The price is a little steep at 1200 msoft points ($15), but after 2 hours and having rescued only one princess, i feel I'm gonna get some serious play time out of an xbla game for a change.
Definetly get the demo (and the Alien Hominid demo while you're at it) on xbox live if you haven't yet (and you have a 360).

this was one of the games i was planning on getting. i finally got the ms points, now i just need some time.

Too bad the online play is messed up, at least right now. most of the time the games randomly disconnect and you cant find any, and in the worst case scenario playing it online might corrupt your save file :o

Well, just finished the game solo, a little sad that a lot of the achievements are online since you guys said the online mode isn't working right
Overall, it took me right around 8 hours to complete it.
The ending was a little wtf, but given the development team behind it, I'm not surprised one bit.
Now that the orange knight (fire) is down, I only have...like 8 more unlocked characters to go and like 20 more to unlock O_o

I love this game I've beaten is with 5-6 of the characters.

I need some help clearing insane mode (its much easier with many players)... stuck on lava world atm with ninja level 99 (got to the boss with a friend once but he died just as I was going to use a potion automatically)

Online play has gotten my 360 to freeze like 6 times already, thats some bad code :P