I've had them on my car since the summer... and I'm quite pleased.
It was the best bang for the buck when it came out(around $640-$750 shipped). However, if someone is gonna pay over $800 for them, I'd tell them to just save up a few hundred dollars more and get a better setup.
If you can get them for $650, I say go for it. You won't find new ones for that price again.
Oh yeah, you might want to see this thread too:
zerothread?id=100791
It turns out that some people have been having problems with theirs... so just be wary of that.