My mum used one for us, I used one for all 3 of my boys, my sister used one for her son, my friends all used one for their kids... guess what... noone has any issues with walking on their tip toes, chronic pain or any of the other so called side effects of using one. I even used a walker with my first, and those play centres for the other 2. In fact Ashton has a tigger jolly jumper and 2 play centres. Am I worried? No!
My opinion is it is absolute rubbish that it will harm your child.
I think you would be hard pressed to find someone who has had a problem for every person that hasn't. I am yet to meet someone IRL who has had issues with them, yet I know more people than I can count on my hands who haven't.
Just MY opinion of course.