On Oct 4, the change to "Turn screen.css into screen.less"[1] was merged and broke the appearance of the installer. It is still usable, but styling is lost. I opened bug #55589 for this problem.
As much work as we've done with Jenkins, this problem shows a gap in our testing -- the web-based installer.
As we begin to prepare for the release of 1.22, I'd like people to start exercising the installer some more. I'm working on finishing up my solution for bugs #42205 (XML support) and #43817 (short descriptions for bundled extensions), but I'd like to make sure there isn't anything missing that I don't know about.
If there are bugs you think I should be aware of before the release -- in the installer or otherwise -- please add me to the CC list and (optionally) send me a separate email.
Mark.