I don't own any, but I've seen some. They're decent cages, the stacking's a plus. The 28x24x12 sized model is around 100 bucks (105 msrp, 95 at LLL) and would be big enough for a corn. You might also check out the Neodesha 3' cage, which base price is 85 something, which includes shipping. This is a bit larger and the door design is more escape proof for any sized snake (I've heard of smallish snakes squeezing out of a vision, between the sliding doors, but that can be solved easily with a piece of felt or something in the crack). Bush is going out of business as of Sept. 1st, though, and the 3' cages seem to be selling pretty fast. The door on that cage is a single piece of glass set in two tracks, so it can be a bit of a pain to open, but you shouldn't have to open it all the way most of the time. The Neodesha doesn't stack. Either cage should be decent.
Other plastic cage companies I've heard decent things about are Barrs, Precision Caging, and Boaphile Plastics.
One thing that's good about plastic: It's WAY lighter than a glass tank.
*note: I do own 3 neodesha cages, two of the 2' models and one of the 3'. All are decent. All have minor flaws in aligning the holes that go through the glass to the lip on each side of the cage, which is where screws go to secure the door. They still get the job done, though, and they're cheap for their size.