if you dont care for GB or even if you do HeXen is always a good one. great customization etc. but i dont know if its out for GB yet im got a new D2G due to pixel issues and am on Froyo with HeXen. im honestly still on froyo with Hexen because im not a big fan of not being able to do a free hotspot. so i like HeXen but the others that have been mentions are good as well
Until I royally ruined my D2G last night with a stupid system mod, I was running the froyo version of CM7, and loved it. I could not find any bugs that were mentionable. Just a few tiny ones here and there, that didn't matter to me. I had to SBF back to box status, and I am now in the process of rooting my D2G as we speak, and putting CM7 back on there. I have used Liberty also, and the lack of sensors just killed an otherwise brilliant rom in my opinion. I have not tried GB, but I haven't heard fantastic reviews for it, so I haven't tried it. I would recommend both Liberty and CM7.