I also capped off my 'Summer of Arcade(PSN)' with the purchase of Castle Crashers, the new 2D Final Fight/Double Dragon/TMNT/Simpsons/X-Men style beat-em-up from The Behemoth, the guys behind the awesome Alien Hominid (also up on XBLA). You can actually play as the Alien Hominid in the game, along with a ton of other characters, as you fight your way through a stylized fantasy kingdom to rescue a gaggle of princesses. It's pretty good. From what I've seen, every character has the same basic move set: light, heavy, jump, block, and magic attack, but their starting weapons and magic attacks differ, which may or may not be just a cosmetic thing; I'm not sure yet.
You also gain XP as you fight along, and when you level up you get some skill points to allocate over strength/damage, magic/mp, defense/hp, and agility/archery. So far I'm playing as the Alien, level 7, and going for max magic (his trusty blaster) and defense. I've read of a bunch of different bugs and netcode problems, but I haven't seen anything yet except not being able to find a game online to join, which could mean problems or nothing at all. Hopefully they'll get it all sorted, and hopefully some of my friends will also pick up the game!
I'm still playing Diablo II, as well. I'm mired (because it's a swamp, you see) in Act III at the moment, trying to kill all the annoying little Tiki dudes and locate the next waypoint that'll allow me to warp back and forth from town--which is important when you're always playing online and the game is re-randomizing every area each time you log on. Oh well, going through each area repeatedly just means more xp and more loot for me, not to mention an easier time later on in the game.