First off, FANTASTIC job on the new containers..
Bit of an issue with PDF files though, as the user experience may not be all it is cracked up to be and is actually out of our hands totally
On a Mac, install Acrobat Reader X - and frankly why wouldn't you.
Now FM 12 gets all that big fat ugly Adobe chrome. (You DO get searching inside the PDF, and lots of other yummy features though)
We use PDF files a LOT, and some of them are post processed to open automatically at the thumbnails page (stops less than quick witted clients from thinking they only contain one page!)
Here is an simple screenshot of an example where a PDF preview container does not even show any of the PDF, and trust me, this will stump the heck out of clients who see this.
Worse still if one of them fiddles about and opens the sign toolbar in this layout is actually impossible to get rid of it or actually do anything else. Believe me, I have tried. Well OK there is a way. Go into layout mode and back to browse. Nope not sure I want a client doing that...