Here's the big question mark for me that hasn't been mentioned here.
There's absolutely no mention of how it will integrate with HomeKit without a Hub. Will it be like the Eve switch which uses Bluetooth (crappy) and is known to be unreliable or will it have an integrated Wifi chip in the switch which you'll have to connect to your Wifi network?
If it's bluetooth, this thing is going to be horrible. I have high hopes since Leviton has been in the business for decades and they won't release something subpar.
I put in a few Lutron Caseta Dimmers and while I'm not a big fan of the dimmer itself, it's rock solid to the point where the on/off functions just like a dumb switch, so if your Wifi goes wonky or the Hub isn't reachable, it will still turn the damn lights on/off.
I can't say the same about the Hue Dimmer. Because it isn't directly wired, I often have to hit the button a few times before the lights turn on and it drives me nuts. I'm now only going to stick to HomeKit compatible directly-wired switches, hopefully with a mechanical (Decora-style) feel (Lutrons are push buttons which are sometimes hard to find in the dark).