I'm twitching to pre-order this phone, but I need to know if I will be able to get through a whole day with just emails and instant messages. I don't even mind getting on GPRS or EDGE Only. Here is my history of phones:
Xperia X1 - with Push Activesync email and NO instant messaging I got about 8 -9 hours (under GPRS).
HTC Magic - I got about 10 hours or so
Apple iPhone - Don't ask. HORRIBLE
Apple iPhone 3G - Even worse under GPRS mode.
Samsung Omnia - about 12 hours, but I didn't try to send lots of messages. It was horrible writing out messages on this one.

By far, the best battery life was given to me by my:
Blackberry 8300 and blackberry bold 9000. Both offering at least a full days worth of instant messaging and push email.

But all I NEED is 18 hours of email and instant messaging and maybe 2 hours worth of music. I'm not big on web browser guy, and I'm not big on youtube. All I need is a device that leaves me in contact with everyone :P My blackberry does that... but its OS is SOOOOOOOOO outdated! It makes me feel old just putting in my password ....