everyone's been complaining about it. I think that it's the firmware. 2.0.1 would probably fix it. Reception is pretty bad too. Even for my wife's 2G iPhone.
Lag was getting all of us with 2.0.
You'll need to "back-up" your phone then "restore" using iTunes.
The auto update to latest firmware function within iTunes did not solve the problem. At least it didn't work early on.
Just restore it and you will see improvement.