Ok, first my "ultimate warm glove system". Outer shell is PI P.R.O. Softshell Lobster Glove(XL), under that is the Gore Xenon Thermal Glove(L), and under that is a Seirus Innovation Thermal Heat Pocket Liner Glove(M). Aside from Bar Mitts which I use regularly on my flat bar road bike, I don't think you can get much better warmth on a road bike unless you use gloves that make you sweat. Granted, you would only want to use all three layers when temperatures are 10 degrees fahrenheit or colder. The fit is tight but shifting is still pretty good considering you have a lobster claw on your hand. I had to take the Shimano Ultegra brake lever pad spacer out of my shifters to increase the distance from the front of my bars to the back of the shifters so my lobster glove would have more room to actuate the levers independentyly. I did this yesterday and a huge improvement from before. The additional layers don't affect dexterity too much. As far as vanity goes, you're going to look silly whether you go with Bar Mitts or a lobster claw glove, but who cares! It' friggin' 0 degrees out.
Tips to keep hands warmer:
Gloves with long cuffs are much better for warmth. If you have a stretchy jacket, pull the sleeves over the glove cuffs rather than tucking the sleeves inside the gloves. That way your body warmth is less likely to escape at the sleeve/glove interface.
Make sure your core is plenty warm. If it isn't, blood will concentrate more around your core meaning less circulation to your finger tips.
Make sure your feet are warm. If not, a message is sent to concentrate blood in core, therby making your feet and hands even colder.
75% of heat loss is through the head and neck area. Close the vent with a Merino Wool Balaclava: http://ecx.images-amazon.com/images/...L._SL1500_.jpg Add a helmet cover like Gore or Sugoi to keep water out and warmth in. Or use a outer shell with detachable helmet hood cover: http://shop.pearlizumi.com/data/uplo...131008_027.jpg. The Rapha winter hat is fantastic also. IMHO worth the price.
Don't eat anything 2 hours before your ride. Blood will concentrate around digesting food. But on a long ride you'll need a power bar or 2 along the way.
Make sure your extremities are warm before you go out. If you start your ride early in the morning, maybe do some calisthenics beforehand to ensure you have good circulation. Your body temperature is usually almost 1 degree cooler in the morning when you get up. Drink some warm liquids before going out.
This may sound a little silly, but keeping your bladder empty will help. Urine is warmed to 98.6 degrees. This excess energy could then be used to help warm the extremeties. I don't have any way of knowing if this helps much or not. But it couldn't hurt. Most cyclists would do this anyway.
And last, but not least, when you close your velcro wrist strap, or whatever, don't tighten it too tight lest you impede the blood flow to your fingers.
Just remember, when the core is warm, excess warmth can be sent to the extremeties. Your vital organs are in your core. That is why the core takes priority over other parts of the body when it comes to heat supply. Use your hands as vents, not your head and neck.
These are suggestions I have picked up over the last couple of years.