It might seem a little basic, but getting this bench has really improved my playing experience. I used to play weddings and rehearsals standing, and I was suffering from back pain. Since getting the bench, the pain is almost completely gone. I find flat benches better than chairs as my thighs are not restricted by the edges. Also, not having a back forces you to sit straight and not rest against the back, which I feel leads to arm and shoulder pain instead.
It is very affordable, light, and can be set for various heights. It might not look like a high end product but mine has suffered quite some abuse and holds up well. I've left in the back of my car for several days at a go, suffering the hot Maltese sun, but apart from some wavy fabric on the underside, it's still in excellent condition.