I'm using EMS to solve a laundry list of problems with my clients.
While barely talked about from Microsoft, one of the most impactful pieces has been the Web Application Proxy. With a 4 mb download and nothing more than outbound internet access on a single server, I can securely share my internal web apps (SharePoint, OWA, SSRS, ConfigMgr reporting, and Service Manager along with various other 3rd party apps) to an iPad in a few minutes with Single Sign On. No VPN or swiss cheese firewalls required. Given that it replaces the need for expensive (6 figures) reverse proxy appliances in that situation, that's huge.
Being early on the Advanced Threat Analytics train, I also can finally answer the old question of "How would you know you've been hacked?" with some confidence. In some early proof of concept deployments, we immediately detected some schedules tasks that were sending sensitive accounts in the clear - we'd have had no idea otherwise that this was happening. Given the expense of other SEIM tools, this more or less came along for the ride. It does seem to answer different questions than some of the other tools out there though, so I consider it more of an enhanced surface area than a direct replacement for other event monitoring tools.
We've also set up automatic RMS encryption of emails based on subject line or who sent it as well as automatic protection of SharePoint libraries, so that as soon as a user uploads the files, it's automatically audited and encrypted just incase it is ever saved outside of where we want it.
In other places, EMS has been a direct replacement for existing MDM/SSO products. Review collected by and hosted on G2.com.