Well, since I'm here.
I caved and bought an Ally a few weeks ago and I've really been loving it over my Switch Lite. Overall it's a great device that is super nice to have the Steam library available along with any other games, retro emulators, etc. My biggest gripe with the device is that it runs Windows and it's not well optimized for its purpose. Something things are rather annoying like sleep, updates, and background software messing with the controller mode.
Super specific but I discovered that adjusting the volume on my bluetooth earbuds caused the controller mode to flip to operating system making the game uncontrollable and the shortcut buttons unresponsive until I turned off the display and woke the device up again.
So they have a bit to go on user experience.
I haven't gotten a chance to run it as a portable PC yet, but I am very interested in how that will work with my portable display. The device itself seems more than capable so it's probably going to be fine to just hook up as a mobile thing.
The device is a beast though in comparison to Switch. But even though it felt a bit bulky in the store which kept me from impulse buying it, it's actually felt very comfortable for gaming on the couch.
I finally started playing Stardew Valley on it and have already put in way too many hours on the game.
Edit: Oh, and I got the Z1 Extreme version.