I've just returned from DebConf (well, about two days ago) and I'm still readjusting to being home after the great time I had in Nicaragua. Thanks a lot to all of you!
So, how things are for now (short version :D):
- everything I've done so far is now merged in the master branch, here's  the commit merging the show_essids branch, now #637128  is closed.
- reproduced #607766 , as expected a the question regarding whether DHCP should be used is shown only for lower than medium debconf priority, so it wouldn't appear in a normal installation, and configuring a WEP network without DHCP fails. It does work just fine with WPA somehow.
- still not very sure what happens with #343269 , the bug reports are a little bit tangled and I didn't yet look very closely into it.