-simple windowmanager (fluxbox, blackbox,fvwm)
-multiuser setup
-native development (fortran, c++)
-programs like xpdf, gnumeric
-properly suspend
I'd vote pdaXrom r198 or maybe Debian.
-Both are easy to get Blackbox, Fluxbox, Fvwm, JWM, IceWM, etc. running on
-pdaXrom multi-user isn't too intuitive, but it can be done without a ton of work (at least I got a second user running decently enough to play Freeciv with). I suspect Debian is much better
-pdaXrom has GCC/G++, I don't think it has fortran. Debian probably does have Fortran, and it does have GCC/G++.
-Both are known to have both programs and other PDF readers (evince, etc.)
-I've only had suspend issues with r198 when using EvilWM (great WM if you like lightweight, in my feed), but fixed them in my version.
If you don't have a big SD to run Debian off of (I think that's how you have to do it), use pdaXrom, otherwise, try both. I'd say stay away from Angstrom if you just want to be a user (also it's GPE, which apparently you don't like (me neither)).