I personally haven't got my hands on one yet.

Here's Tech 21's webpage for the wah:

http://www.tech21nyc.com/KillerWail.html

Take into effect that they will be biased towards their own products. All I've seen so far for this thing is this website and all the catalog listings (Musician's Friend, Sam Ash, AMS etc.) Let me know what you think if you can get your hands...er...feet on one.