I was bummed to see how small the movies and user interface were. I managed to find the high res font option, which helped my ability to read the words. Then I found the UI scaling option, and set it from 1 to 2. Selecting 1 is way small, and 2 is friggin huge!! Surely there must be a way to set it to 1.5 or something somewhere?

This option is not available yet, but it's been confirmed to be introduced soon. So for now you'll unfortunately have to stick to either x1 or x2, but it's coming.

In 1366x768 the UI Scale does not work at all. I feel myself slightly cheated because one of the advised changes was UI scaling at all resolutions.
It is tolerable, as it was in the past, but I´d like to have the 800x600 scaling/aspect size. i´m a fan of big Interfaces.

Yes, not all resolutions offer scaling at this point. If I recall correctly, they will when the update providing custom scales arrives.

The x1.5 (non integer scaling if I am not wrong) is possible to implement but in my experienceis more uncommon that integer scaling in 2d games interfaces etc... Maybe is harder to implement.

But I have hopes in a rework of the interface or in a non harcoded UI implementation, letting easy modifications. It should be even a more critical advance in the engine than the filters or shaders.

Thanks - waiting......

Yes, the updates are rather frequent (though they've lately been working on a larger one) and Beamdog is known for supporting their games for years after release, too.

Is there a list that shows which resolutions that has UI scaling? Because my native res of 1680*1050 doesn't have it and it's a tad too small for my liking.