I think not wanting to waste the money if it does not work could be a factor holding him/her back on the idea. That said the generic two port pci-e add in card that I have based on a Marvell chipset controller boots just fine under OS X like it was claimed to do, in a Hack as it did in the Mac Pro it was in before, I would think an OWC one would as well.
Well, if there is no former experience, I think the only choice is to try or to leave it. "Jumping into the cold water" (can you say that in english?) is not something you can entirely avoid with hackintoshes, especially if you want to push things farther. And I am sure other people would be interested in this too, but someone has to stand up and try or we will never know
Maybe he can actually talk with OWC, explain them the situation and ask if they can return the device if it doesn't work. I think also OWC would be interested if their devices work in a hack, too (at least I would). So the only thing he would loose is some of his time. But again, if time is _that_ valuable and s.o. do not like to invest some of it, I'd say: stay away and buy a Mac. Seriously! (and no offence intended)