Github flavored markdown does do tables (in a manner that's almost equivalent to org): https://github.com/adam-p/markdown-here/wiki/Markdown-Cheats...
Not really, in org-mode, you can compute columns using expressions (like in a spreadsheet) [1]. Moreover, you can feed a table to an (executable) source code block and/or you can store the output of a source code block to a table.
Just to give an example why this could be useful: suppose that you have a code snippet that produces some statistics. You can execute this snippet directly in the org-mode document and have the result in an org table. Then, you could execute another code snippet (e.g. using R) that uses the table as the input and produces a graph that is embedded inline in your org document. In GUI Emacs, you can even preview the resulting graph.
My primary criticism is that the value of org-mode documents decreases enormously outside Emacs.
[1] http://orgmode.org/worg/org-tutorials/org-spreadsheet-intro....
[1] https://github.com/skeeto/skewer-mode [2] And even then, modern cell phones have quad-core 1ghz ARMs on them. I was using org-mode with a P3 600, I'm sure modern phones + a Bluetooth keyboard would be sufficient to run emacs, or at least SSH + emacsclient.
Definitely, that's what I meant. I share org stuff with ox-html or ox-latex. But colleagues cannot really use my org documents unless they are on Emacs.