I used a jolly jumper for DS2, he LOVED it!! DS3 has been having chiropractic treatment since he was a few weeks old for some neck problems so I asked the chiro about them. The gist is that they're not the best, they support the baby in the same way as as say a Baby Bjorn does (all in the pelvis) which isn't good for their developing spine, also they put strain on their legs, so he recommended that they're not so good for babies before they can weight bare on their legs themselves.
Shame as DS is like your little one wants to be held and jump all the time!