For Urban use I really like the Busch and Muller Ixon IQ, with a Planet Bike SuperFlash rear (or a pair of them actually) The Ixon IQ has enough brightness for speedy riding, and a properly focused beam to make the most of its light without blinding other road users. It's AA batteries mean in a pinch you can stop nearly anywhere and get more (though a 20hr runtime on low (plenty bright for most usage, means you'll probably never need to)