UPDATED: Reseting everything, including the router, solved the problem.
After Apple unleashed 2.1 today, and I downloaded and installed it with nary a snag or bump, I thought everything was pretty much apps with my Apps. Needless to say, tonight I whipped out my iPhone's handy Apple Remote App to help out with a little YouTube searching, only to discover that while my libraries (desktop, laptop, Apple TV) were all still set up, none of them would connect. (They'd all worked flawlessly, immediately prior to iTunes 8 and iPhone 2.1).
I removed the libraries and tried to set them up again, but can't get the iPhone to show up in iTunes in order to type in the verification PIN. I'll continue to trouble shoot and report back if I come across any fixes.
Anyone else having this problem?