I set my phone back up like it was on 1.5 when I was getting 2 sometimes even 2.5-3 days.
However, on 2.1 the battery is draining pretty rabidly. I think I will only get about 24 hours max out of this charge, and that is when it will get to 0. I used to charge between 20-30% all the time.
But I do think it will settle in after a few days. It was the same way when the phone was brand new. With a whole new OS, Im thinking the same thing is happening.
Not too worried yet.