I have the Salmon colored version, which is spectacularly beautiful. I usually wear an NRS HydroSilk shirt underneath.
I've only used this thing in the off-season (i.e., when the water is near-freezing). When working hard, it keeps me toasty and relatively dry (still get somewhat wet from sweat -- the gore-tex may breath, but never as much as you'd like). I presume that, if you paddle at a more leisurely pace, it would be adequate if you just wore something warmer underneath it.
The seals at the neck, wrist, and waist do an adequate job keeping most of the water out for short immersions. I use a surf-ski -- so when I capsize, I'm not in the water for long. Basically, for my ten-second or so immersions in near-freezing water, this product keeps out virtually all water. However, if you stay in the water long-enough, it would presumably fill up.
I'm very happy with this product.I bought a new Kokatat Paclite Goretex top, and I have to say, it is incredibly breathable.
I have paddled with it 8 days now, typically about 7 miles each time, and I am like the guy in the H&R Block ad, "I just don't seem to sweat any more".
I have worn a Pnet wicking shirt under it in 65 degree weather, a silk long sleeve shirt and a heavy weight polypropelene top under it in colder weather (in weather between 32 and 50 degrees out) and on one day where there was a moderate rain all day, and I have yet to be even slightly damp underneath at the end of my paddling.
The fit is generous, and range of motion is beyond excellent.
I have a couple of older Kokatat TecTour jackets that always kept my dry, though I tended to sweat more under them. They no longer fit me so well which is why I bought the new jacket. It probably has everything to do with what I am wearing under it these days too though.
My only complaint is that the velcro on the neck closure didn't allow for a secure closure for me. I have a large neck, but not abnormally large. I only had about a half inch of overlap on the Velcro which wasn't secure enough to be acceptable. I had to sew on another 1.5" long piece of 'loop' Velcro, and now it works the way it should.
At first I was leery of how light weight the fabric is, but I am no longer concerned and I like the packability and versatility. I will wear this jacket far more often than the heavier TecTour which I used only when there was very cold water or substantial rain.
This is going to be a great summer/hot weather jacket for paddling on Lake Michigan and Superior where the cold water demands the safety of a paddling jacket, but it won't be like paddling in a sauna. Even the TecTour got pretty steamy on summer days on the big lakes.
I have the Salmon color fabric which I absolutely love the look of. Frankly I have to admit the color alone is what drew me to the jacket on the rack at REI. Their 20% off deal at the time sealed the deal.
I find that this jacket has substantially improved my early spring cold weather/water paddling experience by a wide margin. I would definitely recommend it.