Depends on which gloves you use. I'd say the bar mitts/pogies/whatever-you-call-em make it act as if it's 15 to 20 degrees F warmer than it is. For $17 shipped (in the US at least), it's a great addition to whatever else you're doing. And if you have poor circulation, it means that you can wear less restrictive gloves and still have the same effective warmth. (If you want to see how I modified mine to work with bar mirrors, look here).

Cheers,
Charles