Well, we have seen a few C510's for a while now. From an ATC pont of view they are just in the way. They want to fly between FL350 and FL410 at under .6 mach. Some have been as slow as .52. We just decend them out of the way to below FL310 where the PC12's run them over. Then they scream about not having enough fuel to make thier destination. If you want to fly at prop speeds plan your flight at prop altitudes. If your lucky enough to get higher that is a bonus. At first we climbed them up to altitude and played pool with the aircraft trying to run them over. that got old quick and now we just dont climb them if there is any traffic behind them.