I work on a lot of OSS projects and our company does consultancy. This means I browse other’s projects on a daily basis (i.e. I don’t know the filenames yet). That, combined with the fact that I have a deep love for GUI design and platform consistency, has made me come to the conclusion that something like NERDTree wasn't working for me. I tried to keep on going for a few more weeks, but in the end I decided that writing a file browser would cost me less time than I lost during these few weeks.
I’m glad I wrote it, because now I’m perfectly happy with my MacVim setup, which I wasn't before. I’m also very glad I did not decide to revert to using TextMate or any of the other new closed source editors.
To conclude, it’s a bit of a feeling-thing. I’d invite you to try it out for a while to see if it works for or against your flow. No hard feelings either way :)
PS: It might not be apparent from the article, but the browser provides a few more functions that os x users might be used to in other apps. See the last screenshot: https://github.com/alloy/macvim/wiki/Screenshots.