FWIW, my girl has an e71x, and gets about 3 days per charge...its comparable to my Motorola Q. The 900 should compare to the Droid, and even w/ a slightly larger battery, the Droid can go 24-30 hours where I'm getting only 12-18 under similar conditions w/the 900.

I just started some observations w/my 900 w/3G "off", via the Cellular Disable app., and WiFi "on", logged into my SIP and Skype clients. Preliminary results showing improved life after 5 hours

Even with constant full bars of 2.5G or 3G, by switching manually, it seems like cellular power draw is heavy.