I've seen "Welcome to Macintosh" and of course, "Pirates of Silicon Valley". I've yet to see "MacHeads", although I've heard it wasn't that great to begin with. "Welcome to Macintosh" was pretty good for an amateur documentary, and it had some pretty interesting interviews, although a lot of it was based on things I'd already heard or seen.
"Pirates of Silicon Valley" is of course, a classic. Not only in the computer geek world, but in the business world as well. I enjoy the film because it's the easiest way I can get my friends to learn about this history of Mac vs. PC, without them getting too bored from hearing me talk. The only thing thats disappointing is that the movie is officially outdated (such as it ends on a dark note for Apple, with the line "Microsoft owns part of Apple Computer"). Maybe if there was an update, like an epilogue to modern days, it'd be pretty intersting to see how far Apple's come since the release of that movie 10 years ago.
When I showed "Pirates of Silicon Valley" to my friends (who aren't computer people at all), I actually edited out the ending to make it less confusing specifically the line about Microsoft owning part of Apple. Either way, most of these movies are pretty well known in the Mac community, especially to us geeks. 🙂