I purchased the Reactor Gloves 1 year ago in Size: Medium. They are great in air temps above 45, but at that point, it was nearly as comfortable to just take the gloves off. In 50 degree water and air temp in the high 20's, my fingers were very cold to the point of being painful.
I tried sizing up as I thought perhaps the glove was too tight, but it wasn't an improvement. I do use the gloves for washing the cars in the winter-time, though. The extra motion seems to provide enough blood-flow to stay warm.
I just received a set of NRS Toaster Mitts, though I haven't had a chance to try them out yet.
This is review of the Navigator and Reactor Gloves.
Navigator 2004 Model (Pre-Titanium). Glove is well made, anatomic curve, and tough griptite palm. The 2.5 mm Neoprene makes them warm to about 50 F. Anything below that and your hands may get cool/cold. I have worn them to water temps around 65 deg F before they start to get too warm. Good Glove for the Money (~$26)
Reactor Gloves add another 0.5 Neo and Titanium particles for added warmth. Gloves probably are good to around water temps of 40 deg F and cold air. Good grip, well made, yet not too bulky or stiff. A very good alternative to mitts or Poagies for cold wether paddling. Probably to warm over water temps > 55 deg F.