The lowest temp I commuted in was 7*F (no wind). It can be done and I am always trying new things with my cold-weather gear, especially gloves. In my bin at the moment:

Normal fingerless cycling gloves
Cheapie "mechanics" style gloves
Pearl Izumi full fingers (over-rated!)
Fleece camo gloves (on sale at Dunhams last year)
Old School leather gloves
Ski gloves

These past few mornings I've worn the leathers to work (about 30*F) and worn the Pearls home. The leather gloves will get used the most, they are pretty versatile. The ski gloves are handy when things dip below 20*F. But they can make shifting a bit clumsy.