I can run NumPy, SciPy, matplotlib and astropy on my N900. When I'm in my office or at home, I can redirect the n900's display to my workstation's display (getting the full screen resolution, by redirecting X11 via ssh). I can mount my N900's file system on my workstation via sshfs. When an Android/iOS/WP phone can do all that, I'll start taking one of those platforms seriously. I know Debian or Ubuntu can be installed on an Android device. I've tried several of the methods of doing that on a rooted Nexus 4 that I have. None of the methods I've found result in a usable linux chroot environment that coexists smoothly with Android. If you want a full-fledged workstation in your pocket, as far as I know the N900 is still the best choice. It's slow, but it's irreplaceable.