I think a lot of us have been in the same situation. You're opening this discussion with some of (what I consider) the most innovative and distinguished programmers out there.
Unfortunately, this is entirely a personal decision. If you're compelled by money, sell it. A lot of people are.
Open sourcing things can be awesome. If it fills a popular need, it will be used heavily, and by nature of the community, will be improved upon. Maybe it'll even enter some people's (or a niche) "lexicon" and become standard. That's an awesome feeling, and a great resume point as well. Since you wrote it, you can always provide (paid) support.
I don't think you're going to get a solid "do this or that" from this.