Gentoo has been my favorite so far, after trying mandrake and debian. Of the linux's i've seen the portage system of gentoo is my favorite. Don't get me wrong... apt and rpms are easy too, but with gentoo one command will get you the latest version of kde, compile it with all the optimizations for your architecture, and install it in most of the right places.
the only downside is the compile time. after my initial install of gentoo i needed to get X and kde and all the dependencies for both (qt etc.). the one command (`emerge kde`) took about 15 hours on my 1.5ghrz athlon with dsl.