I've taken my daughter here a number of times and she loves it. Typically, we pay for the use of the ball fort and nothing else, and it's not super-unreasonable. I'd imagine that a party here would be a great idea, but I've never had or attended one. They have a rock climbing wall, an infant/small toddler area, a large ball fort(primary attraction), a trampoline basketball game(for older kids), laser tag, something resembling a build-a-bear station where you can stuff animals, bounce houses, and a laser maze, as well as a number of coin sucking games and machines that will leech you dry. They also have a small food window where they have some gross-looking pizza and pretzels and other junk. I have not tested any of it, so I can't attest to its quality.
When my daughter was three, she loved the ball fort but hated all the noise. It's very noisy inside and a lot of little kids cover their ears when the central air blaster goes off. Now, at 4, she loves it and will run around like a maniac for hours. There are several slides, lots of alcoves and obstacles, and plenty to do. This place WEARS KIDS OUT.
The only main problem is that it's sometimes hard to keep her in the fort. She will walk right out and hover around the games, then beg me to play them. Obviously, this was TreePaad's intent as every quarter counts. But if you are good at saying no to your kids, it can make for a fun time. Caution: gets packed in the wintertime. Also, when you pay for the ball fort you are paying for 2 hours. However, no one has ever come around and checked my wristband or asked us to leave when we occasionally stay for 3 or 4.