Oddly enough, the Maynard is actually quite playable. The frame is standard '90's graphite so it's stiff enough and it's very well made so it feels solid. The down side is that, because of the air tube, it is quite head heavy; probably more head heavy that any racket I've used including the Wilson Hammers. Unless you have forearms like Popeye, forget about modern whipping strokes! On the other hand, if you learned to play in the early 70's, like me, with long, traditional, strokes you can certainly get some power on your rolling topspin forehands with all that head mass behind the ball. As for the stringset flying out, I never had that fear. Once the air tube is pumped up the stringset is solidly held in place, much like a bicycle tube holds the tire in place. The air tube does provide quite a bit of dampening, so I suppose the inventor had that benefit in mind, but it's hard for me to believe the inventor went so far over the top to achieve a modest benefit in dampening that couldn't easily be achieved by making the frame a little less stiff.
Other manufacturers have tried the replaceable string set as well with varying degrees of success. In this Tretorn racket, the stringset is held in place by simply wrapping the frame around it and tightening a turn buckle type screw in the throat. This one feels a lot more flimsy than the Maynard. You wouldn't want to play doubles with me using this racket - I'm always afraid that the stringset will go flying, like a frisbee, on my first hard stroke!