I have some cages that a friend of mine made from hollow core PVC (he makes plantation shutters). For about $50.00 more per cage (on a 48"x24"x15") cage, they beat anything from the manufacturers we've listed - hands down.
The Boaphiles sag, as do the AP and to a lesser extent - the Repti-Racks. They are basic boxes with sliding glass doors with loose tolerances.