Team DeFuse, Fission is the only D2G Rom now and we are all waiting for an update....(not that one is needed, a lot of us are coming from Droid 1 phones where we had updates all the time from a bunch of developers.
The Fission Rom runs great, many themes to go with it. I have been using it for a month and having fun! My D2G runs fast and smooth.
There are a few other teams getting together and maybe we will see some new developers in the future.
i liked fission when it was my only choice, but if you look into the team Get r done stuff you can flash many d2 roms, with the d2g_romer they have created, and run fairly smooth minus the sensors. Im running liberty 1.5 and love it. Even without the sensors i like it better than fission.
flash just means your putting a different rom on the phone. If you tried liberty just by itself it wont work because its for the D2. You need to install liberty then install the D2G_Romer thats made by team get r done. go check out some of their threads.