I really enjoy kayaking! They are light, maneuverable, and for the most part stable.
It has been a much easier time for me using one on a big lake or pond, versus a canoe and paddle. Once you get the hang of using the kayak paddle, you can make better time if distance is a factor than with a canoe, especially in high winds.
One of the big attractions of the kayak for me is the access it provides to streams and areas where my canoe just wouldn't be able to go. I have taken a kayak up some narrow streams in the woods, and been in very shallow water. In one instance I was able to go up over a small abandoned beaver dam with relative ease, and also was able to push it along a shallow sandy bottom until I reached deeper water again.
While I love canoeing, with the storage and capacity they offer, with the kayak I am able to reach remote, difficult areas to access for fly fishing and just general exploring.