@dynamic Debian is much more FOSS focused than Ubuntu. I switched from Ubuntu to Debian, because Ubuntu really didn't seem too concerned with FOSS.
I run Debian testing on my laptop and Debian stable on my server. I haven't had many issues with upgrading to new releases. I just follow the Debian guidelines as another reply mentioned. The biggest issue in the past was with the Nvidia display driver. You also need to keep needed nonfree firmware on USB for install (again documented).
@dynamic I'm a firm believer in usability, but I also know that FOSS is always going to suffer in that regard against corporations in our #capitalist system. I'll sacrifice a little install time in favor of freedom. Debian has been slowly improving in this regard.
Just my perspective. YMMV