We have an inflatable bed in our Fuzion and it is head and shoulders better than any of the fold out sofa beds we've come across. It has a electric pump for inflation and deflation, only takes a couple of minutes to put up or take down.
Part of the mattress fits over the seat part of the sofa and is held in place by Velcro. The rest of the mattress sticks out 90° from the sofa and is plenty long for most people. If you're over 6 and 1/2 feet tall your feet may hang over the edge. :)
4 years and quite a bit of use, most by kids, and no leaks.