Another scenario where the Lync version of busy might fall short would be in a PBX integrated environment and where you have a serial call list, e.g. call first my PBX phone and then my Lync client and if I do not answer send the caller to my voice mail box. Now if Lync did not hand back a busy tone to the PBX you could end up in a scenario where you are busy on the phone in Lync, another important customer calls and he will not even reach your voicemail box. Full story at Kressmark UC.

We recently published a case study with Unify Square that illustrates the value that an MCM certification (or in this case three of them) can bring in competitive situations. Obviously your own mileage may vary but there is one stand out point in this instance that I think is worth noting. The guys at Unify Square are mostly all ex-Microsoft and held senior positions in the UC product group. You'd think that this alone would be the deciding factor for many customers to select them for a given piece of work on OCS or Lync. However, what happened in this case was that it was having 3 certified OCS/Lync Masters on staff that won the business for them. Powerful stuff - and a great endorsement of MCM and the unique differentiation it can bring. Here is the case study for further reading.
http://www.microsoft.com/casestudies/Microsoft-Office-Communications-Server/Unify/Technology-Provider-Generates-ROI-Builds-Business-by-Developing-Top-Technical-Talent/4000009448. Full story at TechNet Blogs.