Although I understand the reason behind allowing XP-skins it is a bit disapointing to see all these high-class but outdated skins uploaded. Not just the IP's but also the XP-only WB-skins that have been uploaded recently.
I am pretty sure that most of the skinners could have asked a friend to test their skins in Vista before uploading them. But as Vista compatibility is not a requirement, some of the skinners might not have seen a reason/incentive to make their skins Vista ready.