The best kernal I've used with 2.7 so far is the Custom Kernal from ROM Manager, as far as battery life goes. Using conservative scaling and keeping it at 245/768, I had great battery life this past Saturday. 3G & sync on, bt off, gps off, wifi off, brightness 100%, after ~12 hours uptime/~4.5 hours wake time, I still had 64% battery left.
The only problem is I'm still getting a drain on the battery while charging and using GPS. I haven't had a chance to pick up a new 1000ma charger to see if it would fix it, but I installed the newer Adrynalyne experimental Undervolt stock kernal two nights ago. This new kernal allowed my phone to charge with GPS/navigation running (still at about 40% the rate it would without GPS/nav) I had to keep IM up to communicate with people from work all day yesterday, which is a lot more than I normally use my phone for. I hope to get a more accurate idea to see how it works after today. So far its stable, but I notice a little more lag than the Custom Kernal. It's not bad though.
kernal link:
http://adrynalyne.us/files/kernels/battery.zip