In a word FANTASTIC!
It's got the grunt of a fourstroke with the agility and simplicity of a stinkwheel.
When the going is really nadgery (trials type terrain) you can run it in a higher gear and it'll pull through without missbehaving or breaking traction. On a 525 on this type of terrain I found you end up spinning the back up and either going sideways or making a real mess of the countryside.
However............. when you want to go banzai, (and the first time you do this you'll cack yersen) get it rolling and short shift into second, get your weight over the front and pin the throttle to the stop. Hang on and get ready to hook third pretty sharpish as the front end comes up to greet you
Repeat untill in top gear. It's totally addictive and like nothing I've ever ridden before (I used to race a CR500)
It's the ultimate jekyl and hyde bike, docile as a kitten when you want it to be and a proper rip snorter when want a blast
The only 2 downsides to the bike for me are the standard tank is too small for more adventurous trail riding.
I think it comes with a 9ltr tank but the 11ltr is much more practical.
The other which I believe is more pronounced on the pre 2004 engines is that they are suceptible to temperature changes. Nothing too dramatic but if you want to keep it absolutely on song then you'll need to alter the jets (a 5 minute job) for winter or summer riding.
You'll probably need to blank one of the rads off too when it gets really cold.
I suppose you can tell I like 300exc's
What year is your's
Edit, doh it's an 06. The guys at leisure trail are spot on for bit's and advice, if you want it to it'll make you R1 seem rather tame.