I purchased pogie bar mitts this fall together with some cold weather tights and a jersey. They are fabulous and make riding when it's cold SOOOOO much nicer. I can wear "regular" (full fingered) mountain bike gloves, so I don't lose dexterity. When it's really cold I throw chemical hand warmers inside the pogies and that will keep my hands nice and toasty down to 25ish degrees for a couple of hours (the longest I'll ever ride when it's that cold anyhow).
I bought these after hearing about the idea of bar mitts. After using them quite a few times this winter, I don't know how I lived without them! It is really nice to not need gloves when the weather gets cold. If it is below freezing I will use glove liners, anything more and my hands get HOT!