Here is what I have experienced driving my YD3203:
Driving down the road at 25 mph+ when I hit a bump or patches in the road the front end jumps around a bit. It is hard to drive with one hand because it can jump so much if you hit an uneven or big bump. I'm hoping hydraulic shocks up front will help this!
I have a ~200 ft. in diameter traffic circle in my neighborhood and when I drive around that the steering seems a bit jerky. It is not linear at all. Going ~20 mph around the circle if I turn the wheel and start going around the circle then turn a little more the front end grabs and turns much harder. I think this is due to the lack of ackermann and that one of the wheels is scrubbing across the pavement at the beginning then at a certain angle it grabs and turns the kart much harder so I have to steer less immediately to maintain my path.
Here is post I put up about correcting the ackerman.
http://www.diygokarts.com/ackermann-post
I've also had an issue the kart under-steering, especially if the road is wet at all! I almost shot out of the above mentioned traffic circle down into someone's yard one day when it had started raining while I was out in the kart. I think that is mainly due to the lightweight front end that Fabroman mentioned above, but my old tires don't help either.

It also did not turn too well in the woods. It often pushed if you had too much speed while trying to make a turn.
I think your kart is going to be wicked fun and fast, but I'm not sure the YD was built to go safely go above 30 mph so you may want to upgrade brakes, suspension, ackermann, etc. to keep up with all that power/speed you'll have.
-T