I want to have a full-suspension bike, but since I already have a XC bike with very light, high-end components, I thought it might be cheaper to buy a new frame that supports rear suspension, buy a rear shock and transfer the hardware onto it. Based on this question – What's the difference between All-Mountain, Cross Country, Freeride, Downhill bikes? – what I'm basically aiming for is an all-mountain bike. I don't plan to use it for ridiculously high-speed descents, just asphalt roads with a lot of varying-size potholes, and the occasional dirt road.
Since there are now MTBs with carbon frames, I thought it was worth looking into such a frame, since it will allow me to build a full-suspension bike that is very light for its class – probably a little over 11 kg. My question is: what are the advantages and disadvantages of riding on such a frame? I'm concerned about durability and anything else I might be overlooking.