I had a pristine (by your definition) 3G - never did anything to my iPhone other than apply the official updates. Today I was forced to do my first restore from backup to get my phone working again. 3.1 has turned me from a happy customer into a disgruntled customer. Unless they fix this problem very soon, I will soon become a non-customer.
Same here. "Pristine" 3G as well for over 1 year with no issues until 3.1.