I have 6-, 8- and 9-speed bikes with just one 10-speed in my garage. I'll be hanging on to 8- and 9-speed as long as possible; I like the feel of greater distance and more solid feel of the shifting. My 10-speed bike works just fine (I use MicroSHIFT bar-end shifters) but I just find myself shifting a lot more. I prefer the less expensive chains and cassettes of 8/9-speed as well.