Nearly everything scales consistently with the changes here. Not sure if we want to fix this here, or in another pull, but there are a few remaining issues when "zoom text only" is checked:

1. The character icon in the scene does not scale.
2. The grid cells don't scale.
3. The character icon in the program block editor escapes its background when scaling (say to 200%).
4. The plus sign in an expanded add node escapes its bound as well.

See screenshot of points 3 and 4.

Those are my notes from testing Firefox, I'll comment separately on other browsers in a few minutes.

Everything scales appropriately and consistently in Chrome and Safari (in both OS X and the iOS simulator). The points I highlighted above work as I'd expect in other browsers, i.e.:

1. The character icon in the scene scales when zooming.
2. The grid cells scale when zooming.
3. The character icon in the program block editor and its background scale together.
4. The plus sign and circle of the expanded add node scale together.

We should talk with Simon about whether we want to rework this issue to be very slightly larger, or break out the remaining fixes. I'd argue for the first, as the testing is very similar for all these issues.

Yeah, I agree that we should rework this issue in a bit larger scale. Also, zooming out also causes some problems to more components than you have noted.