GNUstep is more than ready for "prime time".
It is ready for "prime time" in the Biotech workstation/cluster
environment, which saving lives curing cancer and malaria, is a hell
of
a lot more important than desktops, utils, and fancy UIs.
GNUstep can do exactly what scientists appreciated NeXTSTEP for.
An example would be rapid development within days or weeks of UI's for
remote control of Sun and SGI clusters running complex applications.
Such as Mathematica and MIDAS was used.
With Adun Molecular Dynamics simulator, and many other tools, the same
and more can already be done completely in GNUstep.
http://bioinformatics.org/biococoa/
http://www.moltalk.org/
http://diana.imim.es/Adun
http://www-id.imag.fr/Logiciels/paje/index.html
http://www.inf.ufrgs.br/~lmschnorr/libPaje/
http://bioinfo.med.unc.edu/glabsoftware/page3.html using GNUstep/GSWeb
GNUstep doing what Objective-C was invented for.
The man who invented Objective-C is a Mathematical/Computational
Biologist.
I am a Biochemist, with 28 years research. I work with Biotechnology
everyday.
For serious real applications GNUstep works.