I have one and it has worked great. I've used it on four different trips, all with connecting flights and all traveling alone. If you do get one, I highly recommend practicing with it a few times. It is very easy to get the car seat attached to it, but you have to get the hang of getting the strap back out of it. It isn't hard -- it just requires a bit of yanking.
Another thing I learned after one very bruised hand . . . when you go to install the convertible car seat on the plane (if you go that route) and are threading the plane's seatbelt through the carseat, do two things. Pull the carseat fabric cover down so you can see what you are doing. I was trying to put the seatbelt through, reach around and snap it all together blind. And make sure that the flap to unhook the planes seatbelt is facing outwards and not towards the carseat. Otherwise, if you get it too tight it is hard to unlatch.