iPhone 4 vibration only works some of the time

I'm having an issue where my GSM iPhone 4 will not always vibrate when it should. It seems to be pretty random about when it actually decides to vibrate, so if my phone is on silent I can miss many calls and texts. I tried reinstalling iOS from a backup, and reinstalling from scratch, and neither has solved my issue.

Of course, this happens after my warranty has expired and I don't have applecare.

Has anyone else experienced this issue, and does anyone have a solution?

I'm considering opening up my phone and replacing the vibration motor...

If you're anywhere near an apple store your best bet is to go talk to them about it.