The change from em to pixels seems misguided. Pixels are not a replacement for ems just because it is a programming language. The claim made in the discussion that em is a kludge to make relative resizing possible is wrong. You don't control the users font size to start with. Using ems lets me specify sizes in terms relative to your font size which I do not know. Without ems, I have to force a pixel size on everything to start with, which is terrible (people with vision problems can't read anything now) and which doesn't actually work (setting a font to 10px will not work in my browser for example, I have the minimum font size constrained to 14px). We really do need both px and em to be available.
On a side note, any plans to integrate sounds? The use case I have that got me considering elm was simple web based games like solitaire or connect 4. Sound effects would be really nice there.