I'm using Oxygen 2.0 and it's fantastic. I tried Cyanogen first, but for some reason, I got stuck in a boot loop. My housemate got it to work on his Desire Z (We were sitting around, watching TV with a couple of drinks and decided to finally root his phone and flash some ROMs, just for the hell of it) but didn't really like the way it looked.
I really like Oxygen. It's fast, it's got the beautiful Gingerbread notification bar, and if I decide, for some reason, to stop using LauncherPro, the stock Gingerbread UI is a far superior backup than the frankly ghastly Sense. I don't know what it is about Sense, I just can't stand it, having seen what else there is on offer.
I'm thinking about flashing MIUI, but I'm not entirely sure I like the default icons... is it simple to change them, does anyone know?