Mitts range from 3 layer monsters for standing around at the poles doing nowt to thin, simple shells, so what do you have in mind?
I'm eyeing up the new mitt version of ME's Randonee glove as I've been very impressed with the fingery ones.
I relied on dachmitts for years and the only things wrong with them are they take an age to dry and putting them on wet is like having your hands rasped, but they're Toast Factor 8, still warm when wet and are remarkably good value for money. Put a thin shell over the top and you'd be ready for anything (tropics excepted!). And it's easy to sew wrist loops on...
I've superseded them with Thermal Pro fleece/Goretex double mitts mainly as they have a comfort edgebut thetwo-layer aspect makes them more flexible. It's very handy being able to pull the waterproof shell over gloves as well as the "proper" inner mitts.
Pete.