Hi Vaska,
following up since you are interested in getting feedback. My sense is that those tablet operate in that in between space. In your new theme with larger default text, it would probably be fine; any implementation that uses the standard small text is pretty rough on a tablet.
Now that the CMS is offering responsive, in general, I am wishing that the image sizing under exhibit options offered "image % size"-- it would seem to be much more reliable in the new age of screens large and small, and would lower the stakes regarding when mobile is triggered.
I noticed that the indexhibit.org page switches to mobile just when resizing while my own site and the demo site only switch when visited from a device self-identifying as mobile. I would love if the pixel size was the trigger as the default (or at least a built in option), obviously one can make this happen site by site as well.
Thank you again for all your work, really enjoying my new mobile capability. The update is a great accomplishment for the project.