I have done a fair share of looking into the kite tubes. If I was going to buy any, I would go with the Sportstuff WEGO Kite tube.
Here is the video:
http://www.sportsstuff.com/towables/wego/movie.shtml
Its more steady in the air and I think more useable as a float when stopped.
Its 10' wide when inflated, so you can use it as a lounge.
But with every sport you do on the water, the DRIVER of the boat is RESPONSIBLE for the rider behind the boat!!! You must pay attention to the height of the rider in the air and watch how much control the rider has. If not, You WILL shoot up to over 30', depending on your rope length, at which time flight is uncontrollable and injuries could be severe. There is 1 confirmed death in Texas,a 33 year old man and I think there was a another woman in the south somewhere.
http://www.kfdm1.com/engine.pl?stati...koutlocal.html
So is it dangerous??? Yes. Does that make it fun? Yes. Is it worth the risk?
If you trust your boat driver with being able to watch the rider and watch possible wind gusts and watch where he is going then I say GO FOR IT!!!