Common stuff we have seen are rear wheel bearings, rear axle boots, front suspension issues, valve covers leak, rear main seals leak. We work on quite a handful of these things, also the suspension issues come if they have hooptie wheels on them, which the S models do. I believe they have the 18" Turbo Twist wheels?
Otherwise they are strange to work on with how you access various parts of the motor. For Example having the top half way down to take the panels off to get to the top of the motor etc..
They are quite fun cars, I know a guy with an automatic one that gives the 911 guys a run for their money at the autocrosses.