My personal choice is slightly more fine-grained - I use proprietary software, but will not invest in it, so as to avoid lock-in. I won't use anything that requires proprietary file formats. I use a proprietary text editor, but only because it offers a familiar vi-mode interface. I do a brief mental audit every few months - If I expect it to take more than a day to migrate to a fully-open environment, I know I've ceded too much control to software companies.
I think Stallman is a fundamentalist, but an important one. I think he prompts debate and exemplifies practice in a way that is only possible because he simply will not touch proprietary software. Seth Godin recently argued that one of the most underrated properties of the internet is its ability to show us the limits of what is possible and in that sense Stallman is vital. I see him as a figure like Heston Blumenthal or Ray Jardine - there aren't many people with a sous-vide setup in their kitchen or hiking the Appalachian Trail with an eight pound pack, but their example broadens all our horizons.