It is not bad to work on, but the parts are really expensive for little things that shouldn't cost very much. (spark plug wires - $160-$300) And if you have to order something from a dealer it can take a very long time. I waited almost 6 weeks for special bolts once.
Its fairly reliable, but hard to find people to work on it when something does break. Most likely due to the availability of parts and such.
My 928 runs 14's, which isn't too bad considering how heavy they are. There are not a whole lot of aftermarket parts readily available though unless you want to put a whole lot of money into it.
Car is an absolute blast to drive though. Corners awesome, and its really comfortable.