Your points are valid, but there are other considerations. With open source software I can find and fix a bug in a routine and submit a patch for other people.

Your points are valid, but there are other considerations. With open source software I can find and fix a bug in a routine and submit a patch for other people. With closed-source software, there is no guarantee that a bug I find will be prioritized and fixed if I submit it even if the company values quality (they likely have more open issues than people to fix). Now granted, I'm personally probably not going to track down some obscure bug, but others may.