While, yes, all things will eventually fail, my grandma's microwave that could very easily be from the early 70s or late 60s, still works fine (the door hinges at the bottom like an oven, even!). Things are now apparently designed to fail, but my 6633 failed in just over a year of irregular use (I rarely cook anything for longer than a minute, most of the time when it's used, it's used to reheat things for 35 - 45 seconds). My parents bought one because of the high power and gave me one, too. Oh sure, a free microwave to replace my old one which I then gave away.
The first thing I dislike about it is that it has a large footprint-- I couldn't put it on the small piece of counter between my oven and fridge where i'd had my old one. Bigger microwave? Well, maybe sort of, it's very low so some things I could put in my old microwave don't fit. It's rare that that's an issue, but I never had an issue with anything hitting the sides of my old one, either, so it's just trading off a dimension that was occasionally useful for a dimension that wasn't lacking to begin with, essentially, but YMMV on this issue. It just seems quite large for such a small microwave!
It also heats unevenly. Hotspots, I imagine, are relatively unavoidable, but at one point, my dad put a plate of bacon in theirs and it was charred black in the middle and undercooked along the outside. I don't expect perfect evenness, but that seems poorly designed. I've noticed that with reheating, too.
After finding these microwaves that seem, based on their spec and after a first glance, to be a great bargain, my mom placed a few around her office where they probably saw more use than mine did, and she just told me that all of these units were dead within 9 months.
Oh, and for some reason, when you pull the door open, there's a spot between the fully closed and fully unlatched positions where the microwave runs! I have no idea how this is entangled with the door latch, but to test it I've held the door about 1/4" or so "open" (but not unlatched) and watched the thing go. Very odd. It's like the Gremlin of microwaves-- if it could move, I'd bet that it would die in left hand turns, too.