Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)
I did the update the day after it came out, and don't seem to be having any problems with iTunes 10 using Windows XP.