The Red cassettes are extremely elegant and very durable being all high-strength steel despite their crazy light weight. They work great with SRAM stuff and are supposed to as well with Shimano. The bad rap on them is that they are noisy, because the hollow construction supposedly acts as a sound amplifier. I have had noise problems with SRAM, but in my experience the problem has always been the noisy Red chain, not the cassette. A switch to the light KMC chain completely solved the noise problem for me, Red cassette or no Red cassette. My observation is that the cassette isn't an issue.