@Lucadef
To answer the question of cost of Lync: as of Dec 2012, a Lync Server License costs $3700 plus CALS. See details:
http://windowspbx.blogspot.com/2012/11/microsoft-lync-2013-availability-and.html
Also, remember that this cost doesn't not include implementation, which can easily be as much as licensing for a small setup.
The question immediately comes up, what about Lync Standard Edition (that used to be $699). The short answer is it now costs $3700, below are details:
http://windowspbx.blogspot.com/2012/12/can-i-still-buy-install-lync-server.html
@snomONE (admin)
Since I've been busy with Lync implementations I've been a little sidetracked from snom ONE. I need to say (as someone else did on this thread) that technically snom ONE is an excellent product (so kudos there), but company stability of pbxnsip/snom ONE/vodia is extremely dissappointing, very confidence undermining and I'm sorry to see it.