I wrote mine for a Canadian website. I had it only for a week, and the weather wasn't good, so we didn't ride it as much as we'd have wanted. We compared it to a few other bikes and tried to get a general idea. Here's a link for those who can read French or want to see a few pictures: http://www.motocrossquebec.ca/pages/posts/2010-yamaha-yz450f551.php And for the others, a little recap: Chassis/handling: the new disposition of engine, intake, exhaust, gas tank and rear shock is very noticeable over the 09 model. You get the impression that the bike is much shorter. It's easier to lay over and to maneuver in the air. The rear wheel gyro effect (panic rev, brake tap) is more noticeable. Suspension: rear-end traction is incredible. It's very smooth and stable. I've never experienced a stock suspension that was as good. The front end was pretty good but the stock tire (D742FA) is not very good. The bike is very responsive to sag and fork height. The setting we liked the most after riding the bike for 3 days is written in the link I gave earlier. Ergos: Riding position feels very natural. The seat is flat so it's easy to move around. The bars are a little low for taller riders, but the bend is excellent. The rads are a little bit too wide. Engine: easy cold-starting. A little too much throttle response (yes, now there is such a thing as a 4 stroke that's too responsive) and lots of power everywhere, even at high rev, where EFI bikes usually struggle. I strongly suggest a GYT-R Power Tuner to shape the powerband in any way you like it. Shifting is top notch and the clutch is easy to pull. Exhaust note reminds me of a factory bike. The air filter stayed pretty clean, though there was no dust. It takes a little bit more time to access (and requires 2 wrench sizes instead of one), but it's not more difficult. Fit and finish: excellent, typical Yamaha workmanship. Dirt is prone to get stuck in the area beneath the seat and around the exhaust. The 2-piece side panels are easy to break. Long-term durability is still to prove since it's a totally new model, but I don't see anything major coming out. Overall, it's a great bike. Not so much better that I'd recommend to sell a bike you planned to keep for another year, but better enough to think that if you're in the market for a new 450, you'd be stupid not to at least visit a Yamaha dealer and check it out. If you have questions, feel free to ask.