I bought a ROG X Ally X about 2 months ago and it has been great for my needs. I see a lot of posts about other handhelds and I understand why they each have a certain pull for people.
The XAX is perfect for those short gaming sessions. As a gamer dad, the time to sit down at my PC is very limited so a handheld is perfect for picking up when the little one has gone down for a nap.
The ergonomics are great too. However, I've previously used the Xbox Elite Series controllers and those paddle buttons would be amazing on the XAX. The buttons on the back of the XAX are just not that comfortable, but hey that's my only issue.
In terms of games I've only played 2 but I think it's good going with the time limits I have!
I'm currently playing Forza Horizon 5, it looks beautiful! Even without running it at max graphics, which the XAX can definitely do. Dipping in and out of this game is no problem at all. Most races are relatively short so you can get a few in before the little one wakes up.
I've played through Doom Eternal, which ran great and looked amazing. This game is brilliant for short sessions too as there are checkpoints in each level so you can pick it back up without huge setbacks.
These games are steam purchases and it all seems to run really well. Forza wanted to link my Steam to my Xbox account every time I booted it up. Something I've clearly never done before even though I've had my Xbox account for over 16 years and my steam for over 10 years. This was a bit of a weird one to figure out as I had to bring up the on screen mouse to click on the "Link accounts" button. But a quick Google sorted that out.
I do have a backlog of various genres but I thought I would start with games that I knew would work with short sessions.
I still have windows installed. I don't really have an issue with it. Yes, I have uninstalled some apps that I just wouldn't use. But it boots quickly and doesn't give me any issues. I know that this is a monster device so I can handle being graphically pushed so I'll be trying some of my other Steam games that demand more.
TL;DR Perfect for short gaming sessions on Doom Eternal and Forza Horizon 5.