"Reliable Porsche", tell that to my close friend who had to replace his 996 engine, a few years back, shortly after the warranty expired for the price of a nice car. Not condoning Volvo, but I don't think any manufacturer escapes from build or design problems. I have been fortunate with Volvo's and not so much with BMW's (except their motorcycles) while others have had the reverse. In my view it is just the role of the dice. Sorry to hear about your issues.
I had C70 as a loner the other day. It had only 1500 miles on it. I really hated that car. It was very noisy, and there were tons of rattles inside and a lot of noises in the supension. My XC70 on the other hand is rattle free.
sorry you are having such troubles. FWIW, my c70 remains quiet and rattle free after 11k miles. I find the seats very comfortable and well positioned.
Having owned several convertibles since the 1980s, rattles and leaks are fact of life with topless motoring. It is just a matter of how bad they eventually get (all the more reason for premium sound!). So far, I'm an extremely pleased with the solidness of my c70. I'm sure that it will degrade eventually but so far so good.
I have owned a few hard top convertibles and they are all finicky ... not just Volvo. Best let the dealer do the lube and adjustments (I am speaking of at least the top). I have mine inspected twice a year: spring and fall. While they are in there, might as well let them take care of the rest of it too.