It is time for an update. I posted in 2006 how much I liked the Salsa tostada gloves, yeah they did not hold up to washing at all.
Last winter I purchased a pair of the REI Ridgecrest Mittens They have kept my digits warm down into the single digits. I would really recommend these to anyone.
Equally as nice is a system of layering using OR Goretex shells, over OR Mittens, and then with a thin wool liner. 
I talked about this before… But it is difficult to shift with a heavy weight glove on the bottom, but with a thin wool liner you can do ok.
I have also been using these Craft Split Finger gloves, these are really good down to about 20-25F. After that you have to go mitten… But they do let you shift easily and work just as well on a mtn bike or road bike. The liner comes out making them especially easy to wash, preventing the problem the salsa ones encountered.
You can see I am wearing them in this pic here: 