This is a really important point. I work with someone who has quite a bit of an ego. Definitely cares far too much about his personal brand, which has been built up over the years through open source projects. Any time you work on a project with this person you basically need to use all of his open source libraries if any of them are at all relevant for the project, regardless of if they are the best option for the task or not ... sometimes they are, sometimes they aren't.

By far, the best developers I've ever worked with are quite humble.