Ive got Flexideck. Increased ground clearance makes it a little harder to skate than the GP's but once you get yourself going its mad! Have been 4 wheel boarding for a few years and got the dirtsufer for the extra rush. Dangerously faster than 4 wheeled boards so pad up well (seriously). Less wheel wobble the faster you go, and the rear disc brake works great even in the wet. As for kiting with it, i found it kinda hard without having some one to support you standing up on the board whilst you ready the kite for launch,(it doesnt stand up on its own cos its only got 2 wheels!!), however , in saying that im sure with practice it can be achieved! check out the MKYD .COM website, loadsa dirtsurfing pics, great message board, tips, hints.
If you're unsure on shelling out for a new one, go second hand, you can give it a bash, if you like it then great , if not at least you've tried it and there'll always be someone to take it off your hands!! beware, once you've been bitten by the dirtsufing bug there's no going back.............. 4 wheels are for wimps!!