I wanted to share my experiences with migrating from a C4 to a C7. I had wanted to migrate to a C7 hub for a while, but just did not have the time. So I picked up a C7 over the Christmas break and started migrating my devices. I used the great guide that @bravenel created for migrating Z-Wave devices from a C4-C7. I have about 40 Z-Wave devices and despite taking a while to complete I was able to successful migrate all of the devices without touching any of the apps/rules.
I also have around 50 Zigbee devices to migrate and was able to reset and re-pair all but 1 device to the C7. One of the Iris Motion Sensor V2's refused to reset, so I had to swap it with another and add the new device to a couple apps/rules.
I would say it took at least a good 5-6 hours to migrate everything over. With the Z-Wave devices I would only migrate one at time and then test and remove the old device. Although this was slow, it ensured that I did not forget to remove a device with the old network ID.
I have noticed that the C7 seems to be more responsive overall. Automations also do seem to be firing faster. I am also hoping that over time the hub does not slow down like my C4 did, but time will tell.
To give you an idea of just how much more consistent the C7 is , look at this graph from before/after. You can clearly see a lot of latency spikes with the C4 hub which is almost completely non-existent on the C7 after the migration around Dec 24th.
Here is 30 days.
I really think there are still some large performance issues with the C4 hub that need to be addressed.