I'm wondering the same, I love wp7 and am about to swap my sensation for a lumia 800. Surely it can't be as bad as an android phone like my sensation right? Cause that only lasts 12 hours Max with what I do which is play the odd game, send about 20 texts a day and about an hour or 2 of browsing.
Sent from my HTC Sensation XE with Beats Audio using xda premium
I use my lumia 800 all day, I mean I really use it

:
writting about 20-30 sms
3G internet is on all time becouse I use the phone for business so,
sending 40-50 E-mails /day
The E-mail synchronisation is all time on with instant synchronisation with IMAP server so i instantly get the e-mail when it's arrives
PLay games ~30 min / day
Talking 3-4 hours (3G) /day
Browsing 1-2 hours
And I get 8-9% Battery life at the end of the day.
So like any other smart phone I can say If you use it, you have to charge it every night.
Before lumia i had a C7 (which I accidentally throw out of a window ) It was the same thing about that phone i hadd to charge it every night.
But hey I'm not dissapointed about this, it last very long if you dont browsing sending e-mails all day like me, on hollydays i barely use it, and then it keeps the charging very vell then with one charge iit lasts 3-4 days ( usualy i only make phone calls on hollydays)
Sorry for my poor English
Hope I could give some usable answer

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