I've had the ErgoPlay Tappert guitar support for a long time, but I've started to use it only recently. It's incomparably better than using a fussy and unstable footstool, especially because the free movement of my left ankle is limited, and I cannot hold my foot on the footstool comfortably. Either the footstool starts to slide away or my left heel starts "burning" very soon after I place my foot on it.
Guitar rests are a much better solution to the problem of holding the instrument in a position that's conducive to a healthy body position and easy left hand movement.
That said, every guitar support has its own problems, characteristics or disadvantages that are impossible to avoid with that particular design. ErgoPlay guitar supports work with suction cups, which may be unsuitable on scratchy, matte or uneven surfaces, especially on woods with open pores and a "natural" finish. These supports are very sturdy, with just the right amount of flexibility through the elasticity of the suction cups. Along with that, they tend to be slightly on the bulky side, and they add a noticeable weight to the weight of the instrument. They are also a bit fussy to use, because you need to attach and adjust them before each session and remove them afterwards if you want to put the instrument back to its case. After many practice sessions these routine tasks can become a bit of a chore and they certainly don't facilitate picking up the instrument quickly to try out a musical idea before it gets forgotten.
