I have been getting pretty decent battery life (ususally only down 1 notch or about 20% at end of day). I leave bluetooth on so when I get in my car I am connected. Yesterday, I flew from CA to DC and I had radio turned off for lights and turned off bluetooth since I wasn't using, made only a few calls and battery was way down at the end of the day. Today, I turned bluetooth back on and used the phone heavily and great battery life with less than 10% after all day. I even used the speaker phone heavily today and didn't use it at all yesterday.
if you have a bad signal it'll drain your battery much faster.
That would explain why my battery drains to about 50% after one day (with minimal voice calls but logged into IM all day) - I only get one bar sitting at my desk.