Okay... so an update on this AT&T Messages app...
It works pretty well, especially if you like all-in-one type of repositories for your calls, VMs, SMS, MMS, etc... ( I don't really... but I need Visual Voicemail, this is my only option- it seems to do that part well). It also does not handle MMS well. When I receive pics via text, the app "plays" them in some sort of movie mode... where you can only see it for a few secs, then the pic goes away. Annoying. Plus... when I send pics via MMS through this , the quality is degraded, almost to a point of not being visible to the person receiving it.
It does the threaded group messaging thing okay... and sure works fine for Visual VM, which is what I needed... but if only the rest of the bugs were worked out... I could use it exclusively. I find myself going back to the stock messaging app to send pics.
Grrrr. Not enough to make me regret moving from my 4S... but why can't they get this stuff right!?!?