Is Ubuntu-ARM essentially the same as Ubuntu?

I assume, the major difference is that it, and its included software, can run on ARM, whereas ordinary Ubuntu can't? Are there any other differences?

Does Ubuntu ARM only run Unity 2D? Are 3D effects still supported?

Can Ubuntu ARM be networked? Can it be networked along with other Ubuntu (non-ARM) computers? Is this process the same, at least essentially, as with ordinary Ubuntu?

Ubuntu is intended to be identical for each architecture (currently amd64, armel, i386, powerpc), although there may be some slight differences in behaviour due to incomplete porting to a given architecture (there currently exists no architecture in the archive with no outstanding porting issues, although most are difficult to notice for most users).

Ubuntu Desktop images produced for ARM have included unity-2d as the primary session rather than unity, mostly because there are very few graphics cards available for common armel platforms that support OpenGL in Ubuntu (and none are bundled with common reference devices). I understand that work is in progress to port Unity to OpenGL ES, which is more commonly supported by default on reference devices, which should result in a return to shipping identical images for Ubuntu Desktop.

All Ubuntu documentation, guides, processes, etc. should be the same, regardless of architecture (assuming compatibility of underlying hardware), with the result that if you can achieve some network solution with one architecture (e.g. powerpc), you should be able to do so with another (e.g. armel).

When constructing a network solution with multiple architectures, take care that you have parallel installations of packages, rather than sharing binaries directly between machines: while the same package should behave the same regardless of architecture, in the common case, one is unable to execute e.g. amd64 binaries on an armel host. Packages in the archive have been separately compiled for each architecture to avoid this confusion, so running apt-get install (or otherwise invoking your favourite package manager) will install the correct build of the package.

Probably Unity 2D comes as default because, ARM Netbooks are usually low on graphics.

As for network I don't see a reason why it would not run. Does you hardware support network?

You can try this, i think it might help you: https://wiki.ubuntu.com/ARM/NattyReleaseNotes