Time to begin upgrading components and Sram seems like a viable alternative to Shimano but, are they compatable? I would rather replace my current equipment a piece at a time but, I'm not digging the Sram shifters either. Are Sram deraillers compatable with Shimano shifters? I would also like to know how Sram compares to Shimano Counterparts... Which models are about the same performance etc. Thanks!