When it comes to cycling and winter and hand warming, there's really no such thing as a perfect solution. Many high-tech designs favor a 'lobster claw' design – like the Louis Garneau Super Shield glove ($55) -- especially for extreme cold. However, this type of glove can make it difficult to maneuver with fine finger-to-brake control.
At the other 'extreme' if your hands are stiff from chill you won't have much fine-finger-control either. It's best to experiment, in the bike store, with your bike and the prospective gloves in the same place at the same time. The other problem with gloves is they are easily lost and misplaced, making some of us less wiling to shell out for expensive solutions to the cold fingered-dilemma.
My stop gap measure of the last few years is to wear the thinnest, warmest Thinsulate-style gloves paired with either roomy hand-knit mittens, or even better, roomy wind-stopping leather (also mildly waterproof), like these gorgeous vintage military gloves. A note of caution: in almost all cases, gloves must pass the personal fit test -- try before you buy! (Military gloves shown, $25)