I had one in my backyard for my nephews. At the beginning it was becuase my brother didn't have a yard but then it was just easier to keep it in my yard then move it. They used to beg to come over to play on it, so they got a ton of use out of it. We got a good sturdy one so my nephews played on it for probably 5 years and then I gave it to my godchildren and they played with it for 3 or so more.
I think as long as you buy a good model, add on the safety features (like the netting and pads), take care of it and monitor it's use then it's a good investment.
I also think that part of childhood is playsets and trampolines and pools and bikes. They are all dangerous in a way but you can't wrap kids in cotton wool, kids need play for physical and mental health, and the freak accident component happens even if you never buy any thing 'dangerous'. Literally my very rough and tumble nephews didn't get hurt on equiptment. One fractured his skull walking on the driveway in winter and they both had broken bones (a wrist, an arm, an elbow and an ankle) playing organized sports.