A couple of years ago I found a couple Advance Elements System's Advanced Frame inflatable Single Seat Kayaks on a deep dicounted sale at West Marine, cashed in a bunch of West Rewards and bought the things. West Marine: AdvancedFrame™ Solo Touring Kayak Product Display
I Frankly, I was very skeptical about how good could a 10 foot inflatable Kayak could be but I have been very pleased but with caviats.
First off, no 10 foot kayak of any type will ever paddle as nicely as something longer and narrower. Its simple physics. But if you inflate the Advanced Frame Kayak fully (roughly 5 minutes) it paddles about as well as any 10 foot kayak ever will. I find the seating position comfortable. I have made round trips of roughly 4-5 miles in relative comfort, but mostly do explorations of less than 3 miles. The cockpit unzips if you want an open cockpit layout or closes for normal use (which is how I use the boat. I have paddled in stiff winds and the boat behaved well and with a little care, they handle small chop and power boat wakes quite well. I have yet to ship water. They are light and easy to haul aboard, they don't bang up the boat or leave marks and they are compact enough to leave on deck for short sails. They fit in a compact duffle. Once you get used to it, repacking is a cinch.
Advanced Systems also makes a tandem.Advanced Elements AdvancedFrame Convertible Inflatable Kayak at REI.com
I understand the tandem actually has a way to use it as a single and as such it is a better kayak for covering distances but I have not investigated this boat.
There are some negatives. These are not inexpensive to buy. I think I ended up paying something like $500 for the pair, but today they list for $399.00 each. The tandem lists for $660. These are cheaper than a high quality rigid single or tandem but you can often find used rigid kayaks for sale at much lower prices.
I would also say that a Kayak does not make as versitile a tender as a good dinghy. You can't row out a second anchor or a plant a kedge, or carry 3-4 people ashore. They are harder to get into or out of in a choppy anchorage. They are harder to launch in a surf. They are slower and so anchoring way out and going ashore is a chore. I have stayed dry while paddling, buy I wouldn't count on it as much as I would with a dinghy.
So while I have no regrets about my inflatables, if i were truly looking for a tender, I would get a good dinghy. If I were looking for something to go exploring and get some exercise, the Kayak wins hands down.