Th3 Core

>goes dumb

This is what I'm using
https://www.amazon.com/gp/product/B019HTH2A0/

I haven't fully tested, but I couldn't get these to work unless they had been paired with a hub.  I yet don't know if they continue to function as switches manually if the hub fails once they've been paired.

>why you like it

The highly skilled refugees keep pouring in from Smartthings and development of device drivers and sophisticated "extended" routines (such as thermostat handlers) are happening at what I consider to be a blistering pace for a small tech company.  As it turns out, SH devices are really a sort of white label hardware with readable, modifiable driver files telling them what to do and how to interface with the hub.  So, in some instances, to move a device from one brand hub to hubitat is as simple as doing a find/replace.

<added>
>highly skilled

The user group, being experienced in SH tech, is very good at catching or isolating bugs and actively use the forum to hash it out.  The devs must be sleeping with the code, because I've seen more than a few "Oh, I know the line that's causing this" responses. Then fixed in next update (which are frequent, averaging better than 1/week). 

27 30 devices installed so far, all but 1 are zigbee. Interior and exterior coverage is good.  I have about 8 more devices yet to install, but the mesh is in place and working well. 

require a change in the wiring?

Damn, with all the reading I've done, I keep turning up important layout info buried deep in forums. 

If you have more than 32 ZigBee devices total, you'll also need repeaters since that's the limit for direct connection to the hub (devices routing through repeaters don't count against the hub limit, though each repeater has its own limit as well).

Most items seem to be covered for core functionality,  but may have special features that need a custom driver. For instance,  a switch might also report humidity. It would work generically as a switch but the complete driver would allow it to execute actions as a switch OR humidity sensor.

Hubitat's 'problem' is that it can seemingly use any device if someone writes the driver ...and there are hundreds of devices with more pouring on the market.  But there are favorites,  so they have been operating on a triage system.

No wifi.

I haven't followed it in detail, but I believe some wifi devices are being converted to local network.  Search on TP-Link.

It's confusing at first, all the various SH 'channels.' I bought a few wall outlets and a couple of switches (z-wave, so I ended up not using them). Getting a table lamp to come on at sunset was how I began the trial-and-error & testing phase.