This is no longer the case with displays, so we can choose ourselves, and light on dark is much easier on my eyes (at least it feels like that).
and I think that's why in large classrooms they are still the favourite medium
Personally, I find that if I'm looking at a screen for many hours at a time a darker theme helps prevent eye strain, or at least prolong the inevitable. YMMV, of course.
I've been told this can be caused by astigmatism (which I have), but I haven't spent much time researching it. When I come across a web site with dark background (thankfully quite rare) I use a Chrome plugin that can fix it, and it works reasonably well in most cases.
How does the joke go? -- "Hours of planning can be saved by just a few weeks of coding" or something along those lines. I find a garish eyestrain-inducing theme to incite me to spend more time planning and less time coding.
IIRC, on emissive displays (e.g., pretty much every computer display), light on dark produces more eyestrain with extended use, especially in dark environments.
This is less pronounced with reflective media like paper (at least, in most practical scenarios; you could contrive lighting scenarios with a similar problems, but they don't usually occur accidentally.)
OTOH, Pharo has a very good light theme, even if it's not the default.
BTW, there is the Sublimish Theme that didn't made the release but will be in Pharo 7.
The general take for the next release is to make all of the skinning easier for the system. Like how easy WinAmp was to skin.
Same here. Something about high-contrast schemes irritates my eyes; and I have trouble reading low-contrast text on dark backgrounds, so I've been using black-on-#FFFFDD since I noticed it on the Go Playground.
But it is astounding easier to read black on white in bright settings, like as a passenger in a car. So sometimes I'll use it (black on white) for readability.
Nostalgia for CRT terminals?
This is, of course, quite OT, but what is it with the trend towards dark color schemes? I find that it makes text significantly harder to read. Especially if you sit in a not-very-bright-room.
Other than that, the release notes sound cool. It is good to see that the project is making progress. Git integration sounds very interesting. Source code management was one of the things I found rather confusing as a Smalltalk newbie.