My primary gripe about Petco is how imposing it is. There is no main aisle through the stands around the field; the main aisle behind the lower level is like a dungeon.
So viewing the game on the way to the bathroom or concession stand is nearly impossible. The segmentation/separation of the lower level makes it impossible to spot friends in any level. And heaven forbid you're in seats near the field and need to get out quickly because the entire lower level enters and exits through narrow aisles. This also makes it a pain in the arse when you're watching the game and people are walking about obstructing your view.
The warehouse in the outfied is o.k. but the rest of the stadium doesn't follow that theme. Were they afraid a brick-faced ballpark would seem like another copy of Camden Yards?
The neutral colored stone on the towers and exterior simply lacks character and interest.
Where are the tables/chairs or bar tables/stools to eat? Most folks don't want to eat that 1/2lb hotdog in their seat. Just way too few places to sit down with your grub. And where are the restaurants? There's what 3 of 'em?
IMO it's a nice stadium only because it's new. Once the new wears off I think it will fall out of favor quickly and definitely won't go down as a classic.