I forgot to mention speeds:
They're only very useful if you have different slopes to contend with. The idea when riding is to keep your rpms constant, and adjust your gearing to get the speed you want. For relatively flat terrain, 12 or 15 speeds is fine. To really maximize your ability (and efficiency) to climb, then at the least get 24 speeds. I just looked at mine, and I have 27. I don't really use all those speeds, but they help when I switch between gears as my legs tire out. I alternate the force, but keep the rpms constant when I ride by picking two gears that give me a speed that's about what I want, then alternate between the two as I get tired in one or bored in the other.
BTW, it appears that I have several differences between the bike I showed and the one that is sitting out on my deck.
