I did the recalibration after flashing a new Rom on my u8150 and found it got me back to the correct battery run time from before plus a bit. Just charge it up, delete the batterystats file, run it flat and charge to 100% plus an hour or so and it has performed great. Easily gets 2 days and could do 3 at a stretch if not hammering wifi, gps or data. I think the idea is that the kernel sets the minimum battery voltage (3.6v for 8150) and batteries all charge to about 4.2v so you just set the max and min battery parameters by deleting the old file and forcing android to relearn the voltages in between.

Hardest part was trying to run it flat and charge it up again as it is difficult to find a time that this worked. That and freaking out wondering when it was going to remake the batterystats file, I thought I had broken it when it took a couple of hours to come back.