[dagw]

I think it also depends on which distros you choose. Installing 6 different Debian/Ubuntu flavours, might not teach you much. Installing Debian, Gentoo and OpenBSD will at least open you up to several different ways of solving the same problem.

I also think it really depends on what your end goal for doing it is. Do you just want to get to the point where you have a working dev environment as quickly as possible or do you want to learn about Operating Systems and hardware for its own sake. For me, at the time, getting NetBSD working on a 'no name' PowerPC dev board I bought off of eBay was a fun goal in it self.