ok see thats what i was wondering... im liking the custom roms and i just got AvaZ3 the way i like it and i get great battery life but i keep reading about the GB roms and how great they are. I guess my biggest worry is losing sence and messing something up. I flash alot of sence roms but this is the first time im thinking about a non-sence.
If you decide to flash CM6, don't forget to wipe your device (flash, dalvik, . . .) first.
The CM6 ROM is very fast part due to the low overhead (Sense uses more resources than the stock Android to improve the user experience) and because the Kernel is overclocked.
The downside to running a ASOP ROM is that you lose HDMI and 4G. The 4G can often be added to CM6 with a different kernel. The HDMI is still unavailable. So, that is something to consider as well. My HDMI cable is supposed to show up tomorrow, so that may influence my decision.
Remember, the phone is yours and you should feel free to run it in whatever way suits you. No ROM is for everybody. If you like a Sense based ROM better, stay with it (but don't be afraid to try out a different one).
Out of curiosity, are you flashing ROMs using ROM manager or with a custom recovery like Amon_Ra or Clockworkmod?