mitch, I wouldn't argue with you one bit about the difference in ultimate speed between "normal kayaks" and a "top sea kayak." Our discrepency is only a matter of definition. I'm saying "so-so" and you're saying "normal." I haven't tested enough boats to be qualified as any kind of expert on the subject, but I have read a lot of reviews on paddling net. and in Sea Kayaker. Outside of a very few very specialized super skinny boats, there isn't a huge difference in cruising speed, or top speed in serious sea kayaks. Like I said, about one point something mph.
I guess you could say that in the world of kayaking, one mph is significant, but only if you're keeping score. The way I keep score is how much I enjoyed my last paddle and whether I did it without hurting myself. I've finally figured out that I'm not Superman and if I try to keep up with power boats, a whole lot of my 66 year old body is going to hurt in a couple of days. My new boat allows me to satisfy my desire for a very nice cruising speed and no sore parts. But I still get a kick out of passing a sailboat from time to time.
Oh, and about paddling hard; I've come to understand that there is paddling hard and paddling efficiently. Efficiently--and I can't realy define that--always seems to do the job better and without the pain-penalty of what I would call, "hard paddling."