Don't know about other issues, but I just picked up an 09 500 EFI X2, and the heat shielding on the pipe is a non-problem, at least on this model. They added both a long sheet metal shield under the plastic, and some heat-reflective blanket stuff. Seems to work fine. I've heard some earlier versions did have insufficient heat shielding. '09 and '10 ride is much improved, too, with better geometry, longer travel, and plenty of adjustment range on the suspension.
As far as power goes, I drove 800's and 850's before I bought this one and decided I would not need/use/want the extra power, especially at the expense of initial cost and the penalty in fuel range. Unless one is a member of the young go-fast set (in other words if you haven't yet done a couple of tours in a hospital and a rehab unit after severe get-offs) this 500 has about all the power and torque that can be safely applied to the ground, at least in my estimation. That's just my personal opinion after about 45 years of off-and-on riding dirt and observed trials bikes. I have to admit this is my first four-wheel machine, though.
If going fast is all your friend wants, I'm sure somebody will have a 1200cc 100 hp 90 mph machine out soon, since the power race never ends. And people will buy them.
800 vs 500
