I work with XML files, firefox XML viewer collapse/expand nodes when I click on text, it makes hard to copy text from de XML, I have tried other XML viewers but other problems appear (for example having problem opening large XML files).
The only thing it prevents me for using Firefox is it's XML viewer, clicking on text collapses nodes, it makes copying text very hard. I haven't found a workaround for this.
I'm sure Python 3 is on the radar. But given the choice between spending the time to support 2.7 or 3, choosing 2.7 is a no-brainer. Compatibility for Python 3 has improved quite a bit, but hell, Django doesn't even work on it.