I have a set on my Mustang GT. Back when I was tire shopping they were getting rave reviews on the 'Vette forums so I figured I'd give them a shot. Paid ~$580 shipped for a set of 245/45/R17's from
http://www.tomswheels.com/. Mounting/balancing locally ended up adding $140 to the final cost but I still came in ~$200 cheaper than the same store wanted for a set of Toyo T1R's.
Overall I'm quite happy with them. They're quiet, they don't tramline the road ruts, they're good in the rain, and they stick FAR better than my old tires. In fact at times they almost stick too well - These tires really expose the fact that my car really isn't that powerful. On dry pavement you seriously have to work to break the tires loose. With a clutch dump from a stand still or slow roll you can obviously break them loose but in actual (sane) driving it's very difficult to get anything more than an occasional chirp out of them.
Oh and the look is definitely entertaining too.

It was love at first sight from the tread pattern but I did lots of research before buying. General consensus was they were better than the T1R's I was considering and 20% cheaper. So far they have been great.
BTW feedback I got from another AT'er during my research (who I won't name unless he decides to drop in here):
Those Vredesteins are hands-down the best tire I've ever had. I have about 1000 miles on them with the Z06 and they are just incredible. The response to steering inputs is razor sharp; they can actually hold my full-throttle 1st gear acceleration and they perform very well in the rain. The treadwear is much better than on Michelin Pilot Sports or goodyear F1 Supercars, so I expect they'll last a while as well. Also... these tires are much quieter, and at least with a Z06 that is quite welcomed. Less road noise and more engine noise!
Viper GTS