Keyboard vs. mouse
The other day in a zephyr(*) conversation, the old "I hate this interface because it uses the mouse too much" complaint came out. Almost immediately, someone sent us to this AskTog column, which points out that in studies, people get things done faster using the mouse than the keyboard. To some, this might seem obvious, but to me (and other linux/unix lovers), it seems counterintuitive. The mouse? It requires so much extra movement. But here's the cool part: the keyboard seems fast because the mental challenge of remembering and using all those shortcuts (in my editor of choice, just saving a document requires me to hit ctrl-X and then ctrl-S, and to quit I hit ctrl-X ctrl-C) is significant enough that the user experiences a form of amnesia. The user literally does not remember the (not insignificant) time spent trying to figure out what keys to press. The mouse, on the other hand, seems slow because it's so dead simple, the user can think of other things (like, say, the task he's trying to do) while using the mouse. I was totally blown away by this concept. If you were also, there are two more Tog articles on the keyboard vs. mouse debate: part 2 and part 3.
(*) Zephyr is an online chat system used at CMU. It's ancient, uses UDP, is tied to kerberos, and has no good support from mainstream IM clients. However, the one good thing it has is that each message sent in group chat has a subject as well as a body. This might seem dumb on the surface, but what it does is enable multiple conversations to go on at the same time without all the traffic running together in a nonsensical mess. Most other IM systems use multiple chat rooms to do this, so you wind up clicking back and forth between tabs (or windows, or however your IM client handles it) like crazy to keep track of several conversations. Hey, I wonder if the argument above about mousing being faster applies here too: the work of disambiguating a bunch of text via subject tags makes it seem faster/better than putting each conversation in a separate "place." In reality, maybe the non-zephyr way is better, even though it feels less convenient.