My 2016 played in it in the fall of his junior and senior years. Great event and first class operation by the Rockies--I think their scout team even uses the big-league clubhouse at Salt River Fields on the last day!
I'm partial to the event because it was where the school my son committed to saw him for a third time, then made their offer the next day, but I think it provides all of the players there an extra bite at the apple--like the OP said, there are plenty of schools that attend, and many of the teams that play in it return about a month later for the Senior Fall Classic, so schools can see them again.
It was also the site of one of the most infuriating, but ultimately funny recruiting stories I've ever seen. Son's teammate was scheduled to be the third pitcher in one of the games and had reached out beforehand to a Big 12 school he was interested in. The pitching coach said he'd be there to watch. He showed up at the game, said hi to the dad and was watching...the inning before the kid was scheduled to come in, the coach got up and told another coach he was hungry and was going to Subway for a sandwich! The poor dad didn't know whether to cry or blow up at the coach, but he clearly wasn't happy. All he could say was this was his son's only chance to pitch for the school he wanted to go to and it was being ruined by hunger pangs!
Somehow the coach got back in time to see at least one inning--and indeed saw him again in the Fall Classic and eventually they made an offer. And he's playing there now!