I have a 2011 R8 Spyder
1. Roof Leaks? No leaks, only occasional water drips under a high pressure washer around the window seals. It would, probably better if you replaced the rubber door seals for a tighter seal. After washing the car, you will noticed water on both passenger & driver windows when opening roof.
2. AC Fail? Had a fail of the heater diverter tap, replaced and reconditioned aircon no issues afterwards.
3. Frame cracks? No issues with mine, I've heard it was rectified after MY10 builds, plus spyder had a reinforced structure for rigidity of chasis.
4. Clutch wear? If you have access to a VCDS cable, you can check the wear index to determine the clutch life.
:: Roof Issue? Failed roof sensor & control unit and the roof was stuck in a half open/closed state had to get it towed to a dealer and repaired out of warranty. So if you've got the fidelity insurance, maybe confirm if they cover the roof mechanism.
Gains: Exhaust sound, open air driving and style.
Losses: Increased road noise, no back seat parcel shelf, no room for a subwoofer, No glass engine bay, maintenance harder to get to for mechanics, less aftermarket parts compared to coupe, heavier and slower than coupe.