I have tried some (both hands). They helped the achy wrists but they feel really awkward in the fingers. They weren't tight but I couldn't seem to move my fingers easily. I kept dropping my needles. Maybe it was just me; maybe with a little more practice, I would have gotten used to them.
I started wearing the elastic support that I wear at work (type ALOT) that doesn't have fingers--more like a mitt with a supportive elastic band around the wrist that fastens with velcro. Those work really great for me.
Thanks to AuntCrafty and also SBG. I just ordered a pair from ebay after checking other sites for prices. The s/h for the pair on ebay is what sold me. Hope they work as my hands really do get tired after a stint of knitting.