WLM 2012 suits me fine except for its inconsistent behaviour with mailing groups.  I add my group in the 'To' box, I see the group name prefixed by a +.  I click on the + sign (which is in blue incidentally).  Sometimes it expands to the full list of group member email addresses,sometimes it expands just to a random subset, sometimes to no email addresses at all.  WLM 2011 had no problem with this.

I have found no pattern to this behaviour as yet.  Does Microsoft plan to fix it?  I do have a workaround, but it is still frustrating that the issue hasn't been fixed.