I have had the Primitive 4-puck in my '92 Turbo Legacy for about 7 months now. Does it slip? ahh, NO! Is it a good street setup? That's up to you, there is no doubt about it, it is a race setup. With practice I can usually get pretty smooth engagement, it is really difficult for me to get smooth launches on uphill intersections, as the paddles come into contact with the flywheel/pressure plate I get a surgeing squeeling (similar to a loose belt but lower pitched) mount-flexing doesn't look like I know what I am doing sort of launch
Now, if I use more revs and let the clutch out quicker it won't do it but it will stress the driveline a bit more.
Don't get me wrong, Paul Eklund (owner of Primitive Racing) told me right up front that this is a race piece that 'could' be used on the street if you are willing to put up with the engagement. Paul races his Turbo2.2 Legacy motored Impreza in SCCA ProRally circuit and is a super nice guy to boot!
Having said all that I think Paul now offers the 'ACT' setup which is what all the turbo Impreza guys are using, very civalized engagement with all the holding power and several times more expensive.