We've tested the Quicksilver - it's by the same guy who designed and built the Lectron carbs. It's basically an updated Lectron design with a few frills thrown in.
After testing the FCR and EVERYTHING else on quads and bikes from a Yamaha Warrior (quad), to the XR400 and beyond, I can say there's nothing better than the FCR -- if it's set up correctly!
The flat-slide pumpers are a great step towards near-perfect throttle response and acceleration for most four strokes. All other aftermarket carbs just aren't in the same league.