R52 buying guide

[HappyBoxster]

I'm looking at buying a R52 somewhere in the 05-07 range with 40k on the clock. Are there any good buyers guides/websites/threads that list common problem areas? At this age I am not expecting the car the be immaculate but I would like a little help in identifying the duds.

I would be particularly interested in how well the fabric roof and accompanying mechanisms have aged.

Thanks in advance