Lots of fun.  Kids enjoy it.  One of the balls we go did not hold air, but it comes with 7.  
It took a couple of hours to put together. It wasn't difficult to put together, just time consuming & you'll probably want a break after an hour or so.
TIP: make sure you are paying close attention to the piece numbers & matching up the pieces according to the booklet --- there are two big pieces on the back - can't remember what they're labeled, but they look the same & you may assume it won't matter if you put either on the left or right....IT DOES.  As you move further along in the directions, other pieces will start to not attach properly as the holes will be off, and then you'll have to reverse several directions). Also don't tighten everything really tight from the start....you'll need a little play with the pieces to get them together and if everything is screwed together tightly, it will be much tougher to get pieces to go together.