Bike is pretty awesome and there is a TON of info on those in here that you can search. The 2006 are almost exactly the same, so take those comments into consideration as well. It's hard to know what the one you are looking at is worth without asking the owner a LOT of questions. If well taken care of it should be fine. If it has more than 100 hours on the motor and has never been rebuilt, you might want to factor in the cost of a teardown to check it. If it has 2 or 3 hundred hours, you might want to price out gaskets, bearings, piston, rings, and maybe a sleeve.
+1 on this one. im looking at one myself. any opinions on it. im intending to use it as a commuting bike maybe 1 or 2 a week, weekend blast thru the canyons and maybe the once in a blue moon track day.
Just remember that it is a race bike and you have to treat it like one. It holds 1 liter or oil. Let it warm up before you blast off, change the oil every few hours and check the valves. It is awesome for blasting around on the twisties but I wouldn't commute on the highway with mine. Mine likes the throttle to be wfo or shut. I can imagine trying to keep a constant speed on the highway.
I have a fs650e that I use for commuting, cruising, and the local cart track. I find that with the 6 speed trans it can cruise down the highway very easily, my gearing is 15-38 and I can putt along at 65-70, if your going to do a lot of freeway riding the stock 16-38 would be perfect. For commuting I would recommend the fan kit, this will keep the temps down when at lights or in traffic, other than that I feel they are ready to go.
For once a week commuting (plus weekend riding), weekly oil changes are a good idea and cheap insurance, along with the fan kit just in case you get caught in stop-and-go traffic. Other than that, your biggest problem will be keeping it from getting stolen... I actually thing they are pretty reliable bikes, but don't buy it if a rebuild is out of your budget. All race engines need them, not IF, but WHEN.