First window stays blank when creating a new profile
When Torbutton is installed as a global extension, the first window displayed for a new profile stays blank.
From what I understood by digging the code, that first window is not tagged with __tb_tor_fetched, thus trigerring the defense mechanism in torbutton_check_js_tag().
I do not understand enough of Firefox startup procedure to see how it could be fix. It's not a critical issue, but it's pretty annoying if the homepage is e.g. check.torproject.org.