Interesting that you like metrics. I always consider them B.S. Especially the ones where they say they saved the company X millions of dollars.

Chiming in here -- some metrics are B.S. metrics (like how much money you saved company, I gloss over these myself), but some are valuable. For example: "designed and developed system Foo which ran in production for X years and processed Y events per second utilizing Z nodes."

I agree. Some projects have SLAs. It could be beneficial to mention that those were met or expectations were exceeded.

In some cases saving a company that much money is very believable. For instance if you fixed a transaction processing bug at a company who does $84K a month and it lasted a year, you saved them a million dollars.

I've often wondered how most people do that (metrics, I mean).

I don't feel that I'm in a unique situation where I have worked in groups on projects. The work is divvied up but often multiple people have at least some amount of hands on many things. I feel like there is very little (perhaps nothing) that I can say that I and I alone have done which led to some interesting metric.

Perhaps I'm being overly cautious/team player here? Or do people really mean that they singlehandedly did X, Y and Z to resolve Q? Because to me the latter doesn't sound realistic, at least not at the places where I've worked.

Quantifying yourself is the most important thing you can do in a resume. If you can't figure out what you've accomplished in less than 10 seconds, consider revising.

Yes, regarding reasons for leaving. I'm going to drop those.

DOS and AIX are included to illustrate breadth as opposed to depth. Not because I expect anybody to be impressed by 20-year-old work in these two OSes.

Metrics are an interesting point; I'll need to look further at this.

Regarding teamwork, the resume mentions that I was considered a "mentor". Does this count?

DOS and AIX might well be measures of your breadth, but unless your potential employer cares deeply about that, they don't do you much good. Think of some other way to say "I know a lot of different systems" than mentioning systems that don't garner much modern respect.

I don't mention that I used to frob PDP-11s, nor DOS, nor anything else. There are hints in my resume that I know that stuff, but I don't explicitly say it.

I think that mentioning dead technology creates a kind of taint. Sucks, but there you go.