I used to be much more of an open source fundamentalist than I am now. For me, it's more about trust than source availability. There are closed source projects that I have high trust in, and there are open source projects that I don't trust at all. A project being open source can increase trust, but not necessarily so.

Regarding personalization, I would much rather use software with strong design principles that's simple, opinionated, and works out of the box with sane defaults. I want to spend my time getting work done, not tweaking settings and adding custom features.