After trying a half-dozen timers on Mac OS x, I've finally fond one the that comes (very) close to replacing the supremely useful and elegant Coffee Timer of Mac OS 9 fame from Alessandro Montalcini....

Pros:
1. TTimer actually launches quickly on a 1.33 GHz G4. I wish it would be nearly instantaneous, but it's faster than the others I've tried.
2. It starts the timer on launch--spectacular (this and 1 are useful since my Mac is not in the same room as my tea!)
3. It comes with preset timers for different teas and foods.
4. The default timer is Darjeeling! :-)

Cons:
1. I'm not a fan of metal, and TTimer doesn't interface with any actual device.
2. It doesn't keep counting up to tell you how long you've gone over if you've left the room (ALM's Coffee Timer did), but that's not a must-have.
3. Still takes a bit too long to launch on my Mac, 3-4 bounces on first launch, about 2 thereafter. I miss instant launch of small apps :-(
4. Items 4 and 5 of the license agreement are supremely evil. I suspect they are a joke, but still. Put a smiley face if they are :-)