I will say this, I was using CM7 dailies and also MIUI. They are both Gingerbread roms...and then for kicks I switched to Powerwashed which is a 2.2 based Froyo ROM.
The difference in battery life is huge! I noticed my phone now gets an extra 5 or 6 hours of use using this Naztech battery.
So yes...buy the Naztech...and also you may want to switch to a Froyo ROM that doesn't have all the battery drain issues that the Gingerbread ROMs all seem to have.
Another thing I did that I think makes a bit of a difference, I started unsubscribing myself from all email I get. Groupons, Living Social, Best Buy, Funny or Die, and on and on and on. I would get about 50 emails a day on average. Most of it just junk and ads. I got it down to about 5 emails per day! This is a time saver, and a battery saver. The less I have to screw with my phone for worthless emails, the more battery life.
There are days that I barely touch my phone and it will have been 16 hours and only have used 25 percent battery! No joke.
Love the Naztech battery.