Maybe some of my feelings on this derive from the fact that I remember PI in its hayday. Even before I worked at Disney, I remember walking through PI on family trips and being in awe of the scantily dressed young adults with drinks in hand, the fake tattoo booths, the place where you could make and buy a recording of yourself singing...
At 18, PI didn't hold as much of a draw for me as those crazy Vista Way parties, for sure. But in the post-21 era, it was a great place to go and drink and dance. Shoot, in early 2006 I guarantee you I was there with my friend Mia nearly every Thursday night!
All the same, I understand why they had to shut down PI. In the end, it was simply too big of an undertaking, even for Disney. Too many clubs, for one. They put too much focus on the number of options and not enough on the quality of those options. I truly believe that had they stuck with three places--a comedy club, a rock & roll club (with mainly live music), and a top 40/techno combo club--they would have survived. If they really wanted, they could have worked other aspects (i.e. 80s music) into simple theme nights rather than entire clubs.
Another part of the PI downfall was Disney making it 21 and up. Orlando has plenty of nightlife, and most of it is 21 and up--so PI was great for both tourists and locals. I know that they did this because it was easier for them--less employees needed to check IDs and police underage drinking and all--but if they'd had fewer clubs, this probably never would have been an issue in the first place.
I'm keeping my fingers crossed that "Hyperion Wharf" will feature at least one decent 18+ nightclub for those of us who want to keep the party going past 11 PM...but I'm not going to hold my breath. Le sigh.