This might be just me, but I find it annoying that when I join a new group I suddenly have several hundred posts (at least with well established groups).  Ideally I'd like everything already posted to be marked as unread - I know it's only one click to then mark as unread but it would make me happier!  Has anyone else got any thoughts on this matter?

Default marked as unread: annoying if you don't want it, but easily rectified

Default marked as read: can't be undone if you want to keep track of what you haven't read in that group yet (e.g. recently started groups where you only get a dozen or so new messages and you probably want to read them

I'd go with the one that's easier to correct when its the unwanted behaviour

Leave as is.

As Super-King says, the  option Draigwen proposes obliterates potentially useful information (all for the sake of one mouse clip).... if the users decides to do it thats ok... for the system to arbitrarily decide would be tantamount to 'not playing nice' in my opinion.

Yep, that's exactly what was discussed internally here.

Options FTW.