Well one is that the Control4 has to communicate through the internet to the Nest. So if your wifi is down, your internet is down, or they are having issues anywhere on their end then all communication between the Control4 and Nest is lost. Also if for any reason your Nest thermostats decide to go offline which mine occasionally do then the same thing. You can have events that never trigger or button presses that go no where. In my system I have IFTTT send an alert to my phone to make sure the thermostats actually set to away just in case. Maybe not that big a deal to some but these limitations in themselves are enough to keep me from doing any large system with them. Don't get me wrong I love the Nests but I had them before I had my Control4 system. As far as everything the Control4 thermostats can do I'll let someone who has them chime in.