So nobody even mentions cross-chaining? My 2x6 bike won't let me get away with it. The chain rubs and slips off gears. Some people's bikes don't do those things, but the gears may still be suffering premature wear.

I have down-tube levers on that bike, and I've learned to translate lever positions into gear numbers. (Sometimes, though, I still glance between my feet to see where things are.) If it's not cross-chained, the bike is silky smooth. Happy bike = happy rider.