The 2012 Mercedes S-Class sedans will have 9-speed transmissions. The idea is for them to have the smoothest and quietest shifts you can get.
To me, it’s overkill. Yes, refinement is great, but it is worth the extra expense? Our Honda minivan has a 5-speed transmission, which is wonderful. At highway speeds, it’s purring along at a very low rate of rpm’s. Our Toyota sedan makes do with just a 3-speed. That bothers me a bit, knowing that it would save some fuel if the engine spun at lower rpm’s in top gear.
I remember 10-speed bicycles being an innovation in the USA. My 1972 Gitane road bike came with a 10-speed. I upgraded it to a 12. Today most road bikes have 27 speeds. I’d be happy with 18. (Actually, I am happy with 12 — but I’d appreciate the difference 18 would add to my cycling experience.)