Well, the 1D Mark III is built like a tank, it just works, a truly professional piece of equipment.
The 5D Mark II obviously is not built with the same quality.
The issues with the 1d3 are very well known and covered in most every photography site and forum I know. It was really embarrassing for Canon. Probably their worst blunder ever. Yet, as you say the camera was/is built to a high build standard. It simply had a defect. The 5d Mark II is not built to the same build standard as a 1d3, nor are they made for operating in the same conditions nor were they built for the same service life. But they are both built to a high degree of quality.
My point on this is.. you're praising one body which has a very well known issue, several expensive recalls from Canon, and a problem which has affected the greater percentage of owners. Yet, you're being very harsh on another body with a relatively obscure problem affecting in comparison very few people. It's obvious you're being guided by the degree of inconvenience you've experienced.. and not necessarily the camera. You're not going to influence anyones buying decisions with this sort of logic or presentation. You simply come off as an angry customer.
It doesn't matter how many years you've been a photographer or what cameras you've owned.. This is a consumer problem which requires consumer skills to rectify, and not a photography problem where you're background is in question. If someone with 1 day of experience told me their focus screen and roof pentaprism fell out, or someone with 30 years of experience told me the same thing, I'd believe both. It fell out. It's wrong, it's a defect. Defects happen.
When I said 'heat' was the culprit, I didn't mean at the time it fell out. Most of the people with the problems traced back to some period not long before the failure where they left the camera in a hot car, in the direct sun, or somewhere where it became very hot. I would hope the 5d Mark II isn't failing for the same reasons the original 5d failed..
Your service center should have a list of effective service bulletins on the 5d handy.. same with the 1d3. If you haven't had your 1d3 in for the AF problem you'll probably want to do this. It's something most second hand buyers will ask you about that model. You can do some googles on the issue and go back and read about it, I had no reason so save links.
My experience being around the service centers.. when a customer is obviously agitated they tend to want you to leave as soon as possible and they don't much enjoy 'chatting' with you. They'll go a lot further for someone with a calm demeanor and a real curiosity to identify the problem.
