I'm looking at 3 different sleds, never had a Skidoo before, need some info on the good and bad on these sleds. The 06 Summit is from a private party, has 975 miles on it. The 08 Summit X is a demo unit with 2,000 miles with a one year warranty. The Summit Everest is a demo unit and has 420 miles and a one year warranty. I'd like to know the common issues and any upgrades on these sleds. Thanks in advance.