This isn't really new--it was announced last December and free for the beta period, which was apparently extended but originally scheduled to end March 2018, with a $5/month charge to use the cloud services after that (the first, and perhaps most notable, service provided being Alexa support). They've apparently decided on October for that deadline now, as well as made public some plans for additional cloud features that I'm not sure were previously announced (e.g., remote access to your installation).
I used Home Assistant before Hubitat was announced; I decided to migrate off of SmartThings due to excessive cloud dependency, and after trying a few options (Vera, OpenHAB) that is where I ended up. Like most non-ST platforms, compatibility with many of my ZigBee devices was lacking, but it was adequate and I hoped I could replace the rest with Z-Wave or similar as time passed. But then Hubitat was announced, and I almost didn't get it, having spent so much time migrating to Home Assistant, until I saw many familiar fellow ST refugees behind it-- and I'm glad I did, since it worked with almost all the devices ST did, and I was able to keep using Home Assistant until I migrated my automations off via MQTT (which I also tried on ST but doesn't help much there since it goes through their cloud).
I still have it around, though all my automations have been moved off it--I do like viewing temperature history and whatnot in graphical format, which HASS makes very easy (I'll figure out a way to do that in Hubitat sometime--probably not with webCoRE Fuel Streams, which are otherwise the most promising current option). Hubitat is much easier to configure and use, and more or less just as powerful (though you'll probably never get Python scripting that allows you to do whatever you gave the user it's running as has access to do 
). Most importantly for me, it also works with my devices--most platforms besides ST and Hubitat struggle with ZigBee, and I haven't found any that have a way to allow for custom devices like these two do (though for Z-Wave devices whose behavior is more or less standardized, I could always at least get them to pair and report "things" to HASS and then use templates to get them to display how I really wanted).
Hubitat initially also planned optional cloud services for a similar (identical?) price, but they've since scrapped those plans, and I think Alexa integration was always going to be included "free." If I still used Home Assistant, I'd consider paying that to support their development since everything else is, of course, free, but it's a couple dollars more than my threshold where I'd just do it without thinking about it first (you can host your own Alexa integration if you set it all up yourself, for example--and I can already access my installation remotely via VPN, but obviously this is much easier for most people).
So...I guess I have plans to migrate off HASS eventually, but I used it for a while in between ST and Hubitat. It's a lot more work to set up, but it's powerful, though less widely compatible with (especially ZigBee) devices. Hubitat is much easier to set up and not free, but I'm willing to pay for something (especially still in the lower-end of the consumer range--not HomeSeer prices here) that works well. I'd consider paying for the HASS Cloud if I used it just to support their development, but definitely not as little as I do now.
