Definitely don't use standard rubber comp pads on carbon rims. However, carbon rim pads work pretty ok on alloy. If you swap back, the alloy fragments will tear up your carbon rims - so that's the risk. If you use alloy pads on the carbon rims, they have a high chance of overheating the rim and causing it to warp (and become useless). Especially if they are clinchers - which are prone to this even with the best of pads and careful riding.
Swiss Stop Black Prince are the best (in my opinion) Carbon Rim pad. Period. Expensive - but they result in lower heat and better modulation than any other pad I tried or tested.
A lower cost alternative or the generic Reynolds 'cyro' Blue pads. We carry them as well. They aren't too bad - just if you are planning on extended 70kph+ descents and / or hard - slow braking in the summer, I'd consider the Black Princes.
Carbon Pads are designed to 'shed' - so they'll wear out much faster than alloy pads. I get about 2000km - 3000km depending on riding circumstances.
