Pretty much the same as most bouncy houses out there - the kids run in circles, bounce like maniacs and generally have a good time. The price is pretty typical of these places, although my sister said they have a group discount program, so mom's clubs and church groups could maybe go in together and get a break on the pricing. I noticed a computer center last time I was there, for parents to entertain themselves on while the kids play.
If I were to rate this based purely on the enjoyment that the kids get out of it, it would be five stars without a doubt. Jumpin' Jax is a great indoor inflatable play place. Clean, fun, and good for a range of ages. They also offer wi-fi, computers for parents to use, and a snack bar.
The only reason I won't give them five stars is because the employees are generally pretty out of it. They don't seem to have a very good idea what is going on most of the time.
We had a birthday party there and had to continually ask them for things (such as drinks) that were supposed to be included in the party price, but that the employees forgot about. We ended up over-paying for the party as well because the girl at the desk rang it up wrong. But at that point I wasn't going to try to get her to fix it.