I recently purchased the Viking Bayonet dry glove rings from Bob3, some Atlas 660 gloves from eBay, and some fleece gloves from a sport/moutaineering chain ($4). Total cost after shipping it all to Canada was about $80 usd and includes 11 pair or spare Atlas gloves (would probably be a fair bit less to the US).
I love the dry glove system. My hands never got cold in 47°F water (I'm a generally warm person). I bought them primarily because the dexterity, mobility, and tactile sensations are light-years beyond my 5mm bare wet gloves. For me it was a safety feature.
The Viking system will install on any latex wrist seals, and can be removed without harming the seal in about 2 min (though I don't know why I'd want to do that, hey keep away from my dry-glove rings mister!).
They are dead easy to doff and don by myself, easier than getting my gauntlets on and off of my drysuit arms. They are the only system (apparently) that is certified for haz-mat use as they are sure to seal dry.
An added bonus that my buddies noticed was that they could see my hands very, very easily against the darkness of the water and black suits, making signals even easier to pick up. This is a nice bonus as well (though others have found dips you can apply to your wet-gloves for the same effect).
The only negatives I could fathom would be the increased cost (only pennies a dive), and the fact that you've got rings on your wrist, so you won't be able to reach your hand into as many places as you used to (though it's only slightly larger than the drysuit arm, if you're interested, I could post some pics).
Honestly, I couldn't say enough about the positives, and wholeheartedly endorse the system.
Craig