Interesting thread. Our dishwasher is original to our house, so it's been in service just over 16 years, and I'm pretty sure we'll be replacing it in the next couple of years, so I'm interested in hearing others' experiences with different brands and stores. It still works well, but our well water managed to take what I'm sure was nothing more than a pinprick in the plastic coating of the lower rack, right near the rear wheel mounts, and turned it into a balloon of rust. I expect it could sever completely any day now, and no longer hold the tray level, or allow it to roll in and out.
Replace an entire dishwasher because of a failed tray, you ask? Well, it turns out replacement trays are still available, but they cost - get this - over $400.