there is an atricle about this in the current german magazine c't, and they say that this works, but - as already mentiond in the 1st post - you cannot apply SP2 to a Windows XP HomePro.
As a consequence of this, you can imagine that M$ will maybe apply a "HomePro-Protection" to other security updates - so maybe you won't be able to update your OS any more.
on the other hand, you cannot change back from HomePro to normal Home-Edition - so, this should really only be done for testing purposes, but not on a productive-pc...