I've been experimenting with Wi-Fi sync since the GM was released.
Unfortunately, it's not very reliable; the sync tends to stall out with both sides grinding to a halt and never recovering. That's true whether you initiate the sync manually or let it happen automatically when you plug the iPad in.
And as soon as there's any kind of problem, iTunes removes the device from its device list and won't acknowledge it again until you do a wired sync and turn the "sync over Wi-Fi" flag back on by hand.
I was hoping that the final release of iTunes 10.5 (I'm using the Windows version) would make the feature a bit more usable, but so far the behavior seems about the same.
Needs more time in the oven...