We booked a party for my son's 4th birthday and enjoyed the experience. The staff was very professional and attentive, the pricing was reasonable, and the facility is fun for kids.
Granted, all the kids invited were on my son's baseball team and are baseball players, so that certainly was a plus. Every kid there participated in hitting in the tunnels, and had a good time doing so. This probably wouldn't be a great option if the party invitees were not ball players, but that said, there is a sort of common area that the kids can horse around in when they are not inside the tunnels.
Dad's had fun, too, taking their turn with the pitching machines.