I have finally found the long fingered gloves that will keep my fingers warm and are supple enough to work shifters. While out of town on business I stopped by a LBS and found a pair of the Specialized Sub Zero's in my size. These things are outstanding for colder temperatures. I went on a ride tonight with temps in the 20's and my fingers were perfectly comfortable.
The fingers and palms on the outer shell have a synthetic material on them so that the hands will not slide off the bars or hoods. Because they are a glove inside a glove the fingers are a little larger than I'm used to, but they did not get in the way of shifting. There is also a drawstring on the long cuff that really helps to keep the heat in.
The inside glove seems to run a little on the small size so if you're in between or have longer fingers definitely go with the next size.
These things are certainly not cheap if you buy them retail. There are probably less expensive options using non-cycling gloves that are similarly designed but I just could not find anything else quickly. Based on the results of my one ride I'm one really happy customer.
The rides this weekend might be the ultimate test of these things though.
I've tried several pair of long-finger cycling gloves, but the ones I like best are AXO mountain bike gloves. They keep my fingers warm, but still allow some ventilation so there is no sweat accumulation, and it's still quite easy to work the brifters.
However, they probably wouldn't be warm enough to work in the very low temps noted above. Still, for high 30's - low 50's (F not C) they work great!