I just came off a XC 250 2001 after 2.5 years. It is one of the most tune-able bikes there is. Extremely reliable. Parts prices are are not out of line. Alot of basics like bearings, seals, brakes, air filters, etc. interchange from other modles of jap bikes. Very easy to work on. Trail side jetting is very simple. The difference between the 250 and 300 requires different riding technique. If you ride a 300 like a 250 you will find yourself in the trees. If you ride a 250 like a 300 you will find yourself short changed. The 250 has alot of power and will pull tall gears with no problem, it just requires a bit more activity with the left hand when going up hills and out of turns in a high gear.
But I've recently went to something else and WILL NOT SAY (for LAWMANS benefit) what that Killer-Technologicol-Mojo is ;-)