There's a big thread about these, maybe one of the reviews. I think the consensus concluded that they're still not as good as a VW revision G.
That was after plenty of testing by Nick at R Tech amoungst others.
I suppose it depends how much boost you're putting through it. It would probably be ok on stock or stage 1, but you've got to ask yourself what you're gaining (if anything) for the bigger cost than an oem valve.