I noticed this little gem after upgrading my Lync client to CU5. A very brief poll seems to indicate that this is indeed a new feature. Note the small down arrow below the call button.
Clicking that expands the view so that you can see the entire out of office (OOF, to current and former Microsoft employees) note, complete with a scroll bar if the message is long.
This is a nice little feature that saves me from having to open the contact card to read people’s (sometimes lengthy) out of office notes. Now I just need more people to see these in Lync and Outlook before sending e-mail so my inbox wouldn’t fill up when I’m OOF myself.