I’ve been watching this with interest

Coding Horror: C# and the Compilation Tax
Dennis Forbes – Pragmatic Software Development : Process, People, Programming
Coding Horror: Background Compilation and Background Spell Checking
Knowing.NET – Death and Taxes: Compilation, Type, and Test

My opinion is quite simple. Give people what they want.

If not they will implement it themselves.

I use a workaround. I have three build commands.

1. I’ve just changed some code, and I am not 100% certain it will compile so I want a quick answer. I use F6 redefined to Build.BuildSelection. This builds just the current project and its dependencies. It doesn’t require me to press No because it doesn’t ask me if I want to run the last good result. It just lets me see how many errors and start fixing them with Ctrl-Shift-F12. Its the fastest way I know to compile just what I have changed.
2. I’ve got an assembly building. Now I press either,
   Repeat Test Run from TestDriven.net (Jamie, Can we have a keyboard shortcut please.)
   or F5.
   Either of these will now build just the application I need to run/test, and will detect that I have already built some of the dependencies so it doesn’t spend time rebuilding what it already has. 
3. Finally its Ctrl-Shift-B. This is the checkin build. Build everything. Run all your unit tests, and finally checkin.

It gets me closer to an ideal. I am completely with Larry O’Brien on what I really want, but I am not going to get it until the next version of Studio, unless somebody comes up with a better IDE.