I already have a Z-wave hub for interfacing with home control devices, an AssureLink hub to interface with a Craftsman device, and a Harmony hub to blink IR at the entertainment devices. The Z-wave hub sits on my network, and I can access it directly. The AssureLink hub provides an interface only via their cloud, and can be accessed either from a browser or their smartphone app. The Harmony hub supposedly is Z-wave compatible, but in reality has no external connectivity at all, and pairs only with their remote. My Honeywell thermostat talks only to their cloud, and my Samsung appliances will provide a local interface only to their smartphone app. OpenHAB would be like magic if it could pull all these diverse boxes together.
However, the added complexity means troubleshooting will be an even bigger nightmare. Let's say the Z-wave controlled garage light isn't coming on when the garage door opens. Is the problem in the door opening controller, the AssureLink hub, the local network, the internet connection, Craftsman's cloud, the OpenHAB system, the Z-wave hub, the Z-wave's mesh network routing, the Z-wave light controller, or the bulb itself? The complexity is already outlandish, and the reliability of the mesh network is very poor - adding more complexity will not help it get better. At this point it's not worth even trying to integrate these devices, even though I'd like to.
And I understand what's going on - imagine someone who just pays an installer to plop an integrated box in front of them. They're going to get used to lots of disappointment.