Computable became available on the US store last night and I played with it a little.
Overall it seems to live up to its promise, and works pretty well for a 1.0.0 release.
There do seem to be a few rough spots and bugs, basically no documentation on Computable itself and only web-linked documentation for its components (iPython, SciPy etc.), and possibly over-eager adherence to Apple's draconian anti-downloadable-code restrictions.
The web site suggests there will be a $10 in-app purchase to unlock the full app, but this does not seem to be in place and as far as I can tell all the functionality is enabled for free currently. Again, the lack of documentation leaves some room for uncertainty.
Evaluating an expression (2+2 say) in a new notebook and hen switching to a second notebook and doing an expression there seems to put the Python thread for the second one into a loop. You can press the stop (square box) button on the floating toolbar through.
Attempting to completely evaluate some of the included example notebooks causes various permission errors on some cells (like trying to save a plot to an image file). I don't know if these are bugs or intended security restrictions.
There's a "send" icon at the top of the screen to email a notebook, and a grayed-out "receive" icon with no indication of how one might be able to get a notebook TO Computable. It does not show up in the list of "File Sharing" apps in iTunes either. There's a dropbox sync option in settings but I haven't played with it yet and I believe the author said it's only for input and output data files and not notebooks or Python code.
So it's at least a good start, and highly impressive for the amount of power it packs into an iPad. Probably worth $10 as a portable iPython / SciPy "sketchpad" and as a learning tool for the components like pandas that it does include. If there's no way to add your own Python code or notebooks to the iPad then I don't think it's really useful as a professional tool though.
Given the choice of having only one of Pythonista or Computable I would certainly pick Pythonista today, even though I like the functionality set that Computable includes and will eagerly await further development progress for it.
Wants:
1. Some way to get python code and notebooks to it, even if only through iTunes File Sharing.
2. Local documentation (as in Pythonista for on the go reference).
3. Documentation on the Computable system itself (UI features, etc.)
4. Universal (iPhone) version.
Z.