If you use phone to look at maps you'll kill the battery pretty fast, the screen is a huge power hog, can accounts for 50% to 75% of power consumption unless you are running CPU heavy apps. I figure even with my extended battery I get 4 hours of screen on per charge. Standby I figure 1% per hour with all the network and sync going on, but if I switch on airplane mode maybe 5% per day.

The antenna is also not very powerful, if you have good signal it's all fine (under 10 seconds with AGPS), but once it gets weaker (cloudy days for example) you may find your phone unable to acquire location or take up to half an hour to do it.