One of the big changes with Lync has been Microsoft’s approach of investing in a particular product for a particular function/feature and then have other products leverage that investment. This really makes sense on two levels. First, product groups are not each re-inventing the same wheel. Second, it really makes the ‘better together’ argument more real and less hype.
For example, with Lync 2013, all contact information is in a single Unified Contact Store which is maintained by Exchange 2013. The architecture for that looks like this:
Microsoft has just published an awesome set of posters that illustrate all the current sets of feature integration along with loads of links and more information. I find this a fantastic Lync resource (if only the Microsoft Learning courses were as well described!
You can download these posters (it’s a 9 page PDF) from http://go.microsoft.com/fwlink/p/?LinkId=311975