roms and kernels make bad battery life.

I just did the same thing (came from Evo to NS4G) and get fairly decent battery life (about 12 hours) but not like anyone else here is talking about. Hmmm.. gonna try some of these tips and see.

I know on the Evo, there was a bug in one of the radios that on certain evos (when combined with certain PRI and NV images) would cause high android system usage. You had to flash a different combination of the 3 to fix. I havent seen anything like this on the NS4g yet (actually, havent seen any radio images anywhere... which is kinda weird)
 
Yeah I was looking for a radio downgrade as well and couldn't find any. Every time I had battery issues with my evo that fixed it.
 
Habit after using the evo so long. Darktremors a2sd would make things laggy until second reboot because it had to rebuild the dalvic cache on SD card and do zipalign.