I used it for a month or so at the end of last year & really liked the improved speed, battery life, and some of the tweaks, but missed some of the Sense stuff (e.g. the calendar, the clock, and little things like the fact that if I didn't have 3G enabled & sent a picture message it enabled it, sent, then disabled it.) Every night when I go to bed I switch my phone off - I'm at home, have a land line, and although my mobile almost never rings I don't want it to start in the middle of the night - and put it on charge. That long start-up time the next morning was the main reason I went back.
If the boot time was as short as mine is now, and if I could find replacements for the calendar & clock (tried a few, didn't like any) I'd go back to dGB.