It installed without issues and seems to work just fine on XP here. It isn't supported, so you'll have to accept that and do without any support you might have needed, and it apparently won't be update-able - future versions of X2 tweaked for Win8 will apparently not be installable at all, due to the extent of OS-internal changes, but for this initial release things are basically OK, at least in terms of what I'm seeing here so far.