You can also keep your hands warmer if you make sure that your wrists are warmer. The blood supply to your hands can be warmed using chemical heat packs placed on the inside of the wrists when you know you'll be using your hands alot, and otherwise kept warm using wristlets to bridge the gap between your sleeve and hand (they go up the forearm a bit, similar to legwarmers). If you keep your neck and head warm too, it will help.

Like sleeping bags, gloves won't warm hands, they will only help retain the heat that is naturally present. If you don't have heat to begin with you're not going to have warm hands in any glove. Keeping the peripheral blood flow open and warm is key to keeping hands warm. Reynaud's and other peripheral vascular disorders complicate the issue.

MNS