This is a quotation from Jerry Scharf's email sent to DIY Zoning members:

''..There was a great deal of talk about user interfaces and thermostat looking
things. I propose that a thermostat is a terrible user interface created by
engineers that occupants have been forced to deal with and adapt to. Can
you walk in a room and tell the air temperature? How well does that
indicate how comfortable you are?

There is a great deal of research that show that there are at least 4
things that contribute to heating-A/C comfort. Air temperature, air motion,
humidity and Mean Radiant Temperature (MRT.) So we set some temperature
goal and work very hard to hit that, but have little sympathy for the poor
sod who still feels hot or cold. They turn the temperature up or down some
amount and hope they will now feel better, and then forget about it...

If you look at European thermostatic radiator valves (TRVs,) they have
numbers from 1 to 6 (or so) on them instead of temperatures. Never heard a
user say they would rather have temps on it.

Instead of a setting and displaying a temperature goal, how about "I'm
cold" and "I'm hot" buttons, with a software program to change something
and decay the change to a more normal setting? The second step could be to
start correlating external information (weather) to attempt to predict and
preemptively implement these demand shifts.

It might drive an old school HVAC installer a bit nuts, but I'll bet the
occupants would love it!

Ideally you would use all 4 inputs and apply something like ASHRAE 66
comfort rules to say where the room is at. This is one part of my project,
since I will have measurements or first order approximations on all 4
variables available.''

An interesting note and link provided by Vadim Tkachenko in the same discussion: http://www.hometoys.com/htinews/oct98/articles/sinclair/sinclair.htm

''..Along the same lines - you're talking about user interface now. I was
thinking about what makes devices *good* - it seems to me that there are
two words that would describe the qualities - "precision" and
"confidence". If a device can make the user feel that, the goal is achieved.''