Lync 2011 on the Mac is not feature level with Lync 2010 much less 2013.
Try doing a multi-party video chat in 2010/2011 versions vs. 2013.
Just not possible to see all faces in 10/11 where 2013 gives you a video of all parties at once.
If you are working with remote teams, seeing all parties in one video is a must.
We have three machines now runing the parallels config and it uses a little bit of CPU when the multiparty video is going but nothing serious and never freezes. We've been really happy with it. Works better than some standard native desktops we have in produciton.