After 100 miles paddled, I am impressed with the speed and stability of this tandem kayak. I've assembled it a half dozen times and with 2 people it only takes 45 minutes. It is very straight forward to put together once you've done it a couple times and I don't need to read the instructions anymore.
I've used the K2 to do some 20+ miles open ocean crossings (Long Beach, CA to Catalina Island) and some coastal exploration (Moro Bay, CA to Pismo Beach, CA) and the boat feels very secure in big swells and rough seas. We covered up to 30 miles per day....often waiting for our friends (who paddled rigid single touring boats) to catch up. This boat is indeed pretty fast with 2 people powering it.
I am impressed with the quality of workmanship of Feathercraft boats.