Twit filter seems to me to be the way to go, but only if 1) it's personally selected, not system-wide by admin, karma, or other, and 2) if I don't have to learn another "system" to use it. One switch. Off. On.
Scott, if others consense that a more complex system is in order, may I recommend you build both? I know it's a *touch* more work but I believe a single per-user/per-user switch would be relatively quick. Then you could give us more complex options later.
Just my 2 cents.