check the URL, see figure A, point (7) the units combo box widget. missing from Gimp 2.0.4; verified on athlon-xp and amd64 archs. you'd think someone would have filed a bug on this before I did. not sure if this is a Gentoo Bug or a Gimp bug.
Gimp 2.1.1 reportedly in portage, will report back after testing newer version.
Created attachment 39889 [details] v1, media-gfx/gimp/gimp-2.1.4.ebuild made an ebuild for GIMP 2.1.4, tested it a little bit. everything seems to work. most importantly, the UNITS drop down is working with GIMP 2.1.4 use the attached ebuild if you are irritated by the lack of a UNITS dropdown from GIMP 2.0.4 and are able to test this *development* version of GIMP 2.1.4 understand, i have modified the ebuild so that it downloads from the site without mirroring (RESTRICT="nomirror"). the installed binary is now gimp-2.1
it's in buzilla if someone needs it. closing.