I guess that skyhook is a US only thing as location services doesn't seem to work here in the UK at all. It seems pretty pointless activating it on the wifi only model if it doesn't work here.
It seems to work here in the UK pretty well actually. When Google went around causing a bit of an uproar photographing everyones house at street level, they also logged the MAC address of every router they could see. This is what skyhook uses. It's quite well covered in a small market town where I live.