Welcome to the Droid! You might notice that I've posted about this problem recently. It seems to be fairly common... gmail stops syncing properly, requires that the data be cleared and reset. In my case, I had to do a battery pull on the phone to restore proper syncing. Hopefully better luck with the N1 or Incredible! Droid goes back next week, assuming I don't damage it in the meantime.
Your Droid is not a Blackberry!! Quit pulling the stinking battery! The ONLY time pulling the battery is appropriate is if the screen is completely unresonsive and the power button is unresponsive. A reset can be accomplished with the keypad, pressing control-alt-delete at the same time (note: control is the arrow button to the left of the Z)
A battery pull DOES NOT "restore syncing". Resetting the device may do this. And resetting the device is accompished in ways other than battery pulls. Battery pulls for no particular reason may damage the device.