Have a few short days at the track on this bike. I can tell you that it handles great. It seems to be very light, turns great, and suspension is as good as everyone is saying it is. Center of gravity is low and balanced. The bike is forgiving, changes direction easily, and jumps well too. Brakes and clutch are also great. Light clutch pull is awesome, despite stiffer clutch springs in the 06 due to a new lever ratio. Brakes are among the best that I and my friend (4 year pro) have felt. Transmission shifts like butter. Hope it holds up.
Plastic guards in front of the engine seem like a week link as does the included skid plate(will dent if you put your bike on the stand wrong). Ergonomics are spot on for my 6'2" frame. Seat is flat and easy to move around on, as well as cushy(not found on yamaha) and has good traction. Plastics look cool in my opinion(may cost more though) and the clean/minimal graphics too.
The engine is my only concern. The power is there and strong. All my thoughts compare to my old 03 yz250f. The 06 kx engine starts easily and vibrates less than my yamaha. The power is good in my opinion, smoother than the yzf, but without the midrange hit. At first the engine was popping quite a bit, especially when decelerating. My pro friend who recently got 6th in the pro class at Mammoth mx this year says the bike is REALLY fast and he loved everything about it. A lot faster than his 05 rmz250. I wasn't as impressed with the power. My brother also rode the bike and said that it is TOO fast for him(beginner) and wouldn't want it ANY FASTER at all if he owned it, and that he liked my old 03 yz power better saying it was easier to ride(I found this strange, the smoothe kx250f power is super linear). The engine should be way more reliable than in previous years, as well as the transmission. I hope its as reliable as the yamaha's Fs are, fact is, they ARE the best.
Then I got a great deal on a two bros exhaust and the popping came back. Power under accel is great, but off the gas, lots of annoying popping. Two bros says use stock jetting, so I looked at some problems that 05 owners were having. Some say the popping is due to too lean of a pilot jet. I tried turning the pilot screw out 3.25 turns, and the popping has all but barely gone away. I will try the recommended 42 pilot that cures most 05 problems. Hope this helps.
Overall, it's a very fun bike to ride. People seem to really love this bike. I 'm sure it will be right there this year. i will follow up with photos and more info.... Matt