I read somewhere that when you update, you gotta let the kernel settle in for a day or two (maybe more).
NC1 contained a new kernel.
Right now I'm running a custom ROM (but with another base), but the kernel is stock NC1.
Long story short: with power saving mode on and all connectivity off (wi-fi, 3G, Bluetooth, GPS) off, for 8 hours the thing lost 1% battery.
But, alas, some one hour of browsing on wi-fi, and it fell down to 88%.
Don't ye worry, folks! Graphene batteries will hit the market in several years, and our phones will last a week on a single charge with heavy use, and the charging time itself will be 5 minutes!
(Or at least that's what the science news tells us.
)