I think you have really summed up the value of a project manager. A good project manager will be able to (with the help of devs and QA doing estimates) put things in to 4 week sprints or whatever system you are using and, with the help of management, prioritize the tasks so that the most important ones get done first. They should be able to explain to management and end users the time constraints and make sure they understand that sometimes things are not as simple as they think they are.

I've had experiences with both the good and the bad. My first software project went through 3 project managers before I quit and moved to a different project. The first PM worked remotely and I never really met him at all. The second was a decent manager but his strengths weren't in software project management so he wasn't really good for the project. He also had too many long meetings (45 minute "stand up"?) which wasn't helpful and felt like it just wasted our time. However, he was a really great help for me professionaly, so, I like him. The third PM seemed to be moving the project in the right direction but I didn't interact with her much. When I moved to a software company I encountered a much better implementation of the Agile method and a PM who knew how to run a quick stand up and help us find the tools and help we needed to move forward with the project. She was great. We just hired a new PM to replace her and so far she has also been a great PM. So, I've had the good and the bad so I can see how some mid or upper management person would think you don't need a PM or why a dev might get frustrated with the process. But, at the end of the day, you need a good process and good design. It is really hard to do that without someone taking on the role of project manager.

I've done QA and I moved to development. The jobs are very different. Devs should check their own work and write unit tests, obviously, but QA really is it's own step and should not be minimized. Sure, you can code regression testing and unit test just about anything in the right environment, but a good QA tester will do things you will never think of and catch a bug before it is found on production.

Actually, it seems that Mac users are getting a hell of a lot sicker. Maybe they are taking a page out of Nick Naylor's book: "Although we are constantly exploring the subject, currently there is no direct evidence that links MacBook usage to brain cancer."