I use first gear heated gloves. They are effective for me, and I have ridden pretty close to 0* and rain and fog and snow weather for an hour at a time with no issues. The down side is they are fairly low quality and I've had two pairs stop working in two years. And it doesn't take them long to break down and start leaking air, making them pretty useless below 45* or so if the heaters aren't on. Their warranty was OK. They replaced one set outright with the same gloves, but on another pair they could not figure out what was wrong with them so sent them back unchanged.
I borrowed a friends Gerbing heated gloves once and liked them much better for quality and comfort, but another friend told me he got screwed by their warranty. They gave him a much cheaper replacement and refused to give him a comparable item.
If I had the dough laying about I'd try Alpinestar's heated gloves. As it is I'm more interested in Gerbing's so I can get the matching jacket and pants. I tried my friend's whole suit in about 20* and it was such high quality that I didn't even need the heaters - when I turned them on I immediately started sweating. Which was a good thing since they blew my undersized fuse 15 miles into the ride.
Side note: I also have Gerbing's heated insole inserts, but I do not like them because the wire comes out of a huge bulge in the insole directly under the arch of your foot, which for me made them more uncomfortable than cold toes. Good arctic wool socks did more for me.
http://www.motorcycle-superstore.com/14/67/904/10884/ITEM/Firstgear-Heated-Rider-Gloves.aspx
http://www.motorcycle-superstore.com/14/67/904/40985/ITEM/Alpinestars-Tech-Heated-Gloves.aspx
http://gerbing.com/Products/Gloves/G3.php
http://gerbing.com/Products/insoles.php
Another side note: No matter what you have, the heat-troller or comparable gadget is definitely worth the extra money to dial in your comfort level. I have a regular on/off switch for troubleshooting/backup, and when I have used that in less than extremely cold conditions I find myself fumbling for the switch every few minutes and always either being too hot or too cold.
If you care about such things, I will point out that firstgear has a three year warranty and are made in China, while Gerbing has a lifetime warranty and are in the process of moving all their manufacturing back to the USA.