It appears the Steam Machine is much more powerful than what a typical mini desktop pc would offer, while staying cool and quiet.
Gamers Nexus review: https://youtu.be/66QzlDewigE
I love my Steam Deck but let's not forget that it took a solid 2-3 years for it to really become a somewhat turnkey, stable experience. They shipped it in a near-beta state. Flipping between gaming/desktop mode induced a fail state probably 30% of the time until a year ago, docking to TV's can still be very frustrating (aspect ratio and latency are almost always wonky until you tinker with it a fair bit) and isn't nearly as smooth a transition as with the switch, there used to be a VERY frustrating lockout where if your deck wanted to update and you weren't on your home network it wouldn't log in, just all sorts of really frustrating points of friction.
Again I love my deck, it's an incredible and capable device. But it was very clunky those first 2-3 years. It really only matured in the last 12-18mo or so. Hopefully the SM is a stronger experience day/week/month 1.
I got the Steam Deck on release. It was a near solid device for me from the get go. Only had the occasional crash/reboot, but I wouldn't describe it as having been clunky.
I love it and use it a lot, but it's not a Nintendo Switch experience, at all.
I got my deck fixed after the warranty period, for example, with very little fuss. They even payed for the shipping of the broken device to them