We have a fairly large enterprise with a multitude of VOIP installations including solutions from Cisco, Nortel, Avaya and NEC. We have deployed Lync and are currently using its VOIP and desktop videoconferencing.
Personally I am a teleworker and I use the Lync solution as my primary voice, videoconferencing, IM, presentation and collaboration software. I have a Polycom handset that is attached to the Lync infrastructure. It is very reliable. The odd time I have an issue it is typically bandwidth related (due to my own ISP provider or local congestion).
From an end user experience I would say it is good. That being said, from a technical perspective (I am a network manager) I do have concerns with the complexity of the Lync architecture and the fact it is still a bit green in the Enterprise VOIP space. It has definitely improved over time with the releases (Microsoft OCS, OCS R2, Lync 2010 and now Lync 2013)
Microsoft has a pretty good product and is a viable competitor to other vendors for certain customers. I say certain customers because it is complex and expensive as you add on all the bells and whistles.
