We love this place! We come to Arizona every year or so to visit family, and this is the hands-down favorite park for my boys (6-year-old twins). It helps that they LOVE trains, and I believe we rode the train five times (or was it six?) in one day. And the carousel four or five times too. We bought the all-day pass for all four of us, $7.50 each, and that was well worth the money. My boys even rode in the caboose a couple times (aka the "jail" or so they dubbed it).
The playground is phenomenal, but the real star is the train. At about 10-12 minutes per trip, it's well worth the $$ for one ride or all day!