It all depends on how it was ridden, and whats been done. A few things, look at the rear suspension arms in the skid for cracking of the welds. Not a deal breaker, and the fix/update can make them stronger than original.
Check the wire from the shock for breaks, splices, tears, and when running, majke sure the display shows the shock adjustment when using the thumb swithch.
Lift the front of the sled off the ground and check the front A-arms for bushing wear. If no wear is noticed Ulmers kit is a good upgrade anyway.
Check to see if the inner bogey wheels towards the front of the skid have been updated/replaced. The '06's came out with a wheel that had a softer rubber that de-laminated easilly, and the warranty/upgrade was to install the harder wheels. If they look to be all plastic with no rubber around them, they should be fine.
Other than that, just normal wear items, Clutch sheaves, track condition, etc. Also check inside the panels for corrosion on the aluminum surfaces that may indicate being trailered on an open trailer. I did that with mine, and it made alot of work to tear the sled(s) down and remove that "scale" from salty roads.
2500 miles isn't too many for sure on an '06.