Commuted with my new Blackburn Flea today. Its a great little "be seen" light, as opposed to more powerful light that you would need to see the road in darkness. Its super light (17 grams), bright (for its size and power), and is easy to put on and take off the bike.
Another great feature is that it is rechargeable from any 1.5v battery. It comes with two wires with little magnets on the end that let you instantly connect it to a AAA, AA, C, or D size battery for charging. Neat!