Having been on the other side of a Skype for Business installation I can tell you that it is extremely variable and can scale anywhere from a self-contained single server set-up[1] to a multi-region, multi-fail-over-cluster, highly available, extremely complicated set-up[2]. We had a few issues post initial install but spent the time to track them down to the point where our system was reliable and more usable than web ex and it's ilk. This is the crux of Lync, so much depends on your required set up and how well that was done.

[1] - http://bressner.com/ucbox-express/ [2] - http://go.microsoft.com/fwlink/p/?LinkId=550989