Tried the Quicksilver Heated Vest today. Wind chill of 32, 20mph North Winds, water temp 49.
The Heating area is in the perfect place for a Kiteboarder, as the harness presses it up against your back. With only 2 hours of battery life on the low heat setting, I started out initially on low, hoping to ride for 2 hours with a warm back. The vest definitely produces some warmth. It's not super hot and toasty, but more like just a little warm. I found that the warmth just wasn't quite enough. The vest definitely did not meet my expectations, prior to the ride.
The battery is really the biggest problem with the suit. The battery is not only a battery, but also the controller for the heat. It is pressure activated, so as you push in on the top of the battery, the battery vibrates once to signal low heat. As you push the battery again, the battery vibrates twice for high heat. The battery is thicker than you would like (around an inch) and sits right in between your lower ribs and your harness. There is no way to describe this except VERY UNCOMFORTABLE. No matter how hard you try to move the battery under your wetsuit, you simply can't take away the pain of a blunt object being pressed into your ribs every time you lean back. On top of this, each time I loaded for a jump, the harness would apply enough pressure to activate the controls on the top of the battery. The end result, each time I went airborn, the battery (which was pressed hard into my ribs) would vibrate once or twice. WOW!
Needless to say, not a product for kiteboarders at this point. I got out of the water after 30 minutes, just to remove the vest and go back out. The warmth was noticeable, but not warm enough to be worth the discomfort from the battery. I won't wear it again. It's going on Ebay, ASAP!