Hi, I have "transitioned" my own family, in-law, and a few friends to GNU-Linux, including complete Noob. I had the best results with Ubuntu LTS, it's really an important point to stick with LTS, and Mandriva (be careful to stick with official repository, no "testing" or "backport", it would be nonsense for Noob).
As for Kubuntu, it used to be borderline crappy, but since 9.10 it's getting in good shape and it's now up to Ubuntu standards, I have good feelings for the coming LTS "Lucid Lynx" if the transition can wait until then.

Don't try to make it "windows-like", you will lose your time in stupid customisation, it will break on upgrades, and the user will always be looking back with the feeling that "it ain't the same". Linux is NOT Windows, that's why it's so much better, just go with it and don't try to sell it as a Windows placebo.

Other good choices are OpenSuse (I avoid it for "ethical" reasons, not technical ones), Debian Stable (but will take longer to configure to your needs). Lesser known distro are often to avoid for new users (less assistance, on-line resources, fewer packages...), one exception I used is Mepis.

f-spot like it's friend tomboy drags tons of "mono" packages, which is of no interest to users and free software in general, maybe scraping this would help saving space for The Gimp ? Besides, f-spot sucks, it's nowhere near Digikam that ships with KDE, and it's not playing in The Gimp category. Most Ubuntu users I know use (non-free) Picasa® or Digikam together with The Gimp.

Well, looks like Ubuntustudio http://ubuntustudio.org/ really serves a purpose...

Or maybe Ubuntu should just ship with "Applications" menu icons that just trigger the "Ubuntu software center" on the corresponding software when clicked, this way the .iso stays light, but user still get a chance to discover the very nice program that The Gimp is.