My deck has actually ruined gaming on my desktop for me in a lot of ways. There are some games that are just a LOT better on on the deck due to the controls and having the screen right in hand. The gyro controls on the deck are great, and they make a lot of games that I would normally never consider playing on a controller very playable, and in fact even more fun than with mouse+keyboard. (Mass Effect for example)

Metal: Hellsinger is another one that's just great on the deck. It feels way more kinetic to be on the deck with motion controls than sitting waving your mouse around.

As far as ergonomics go, I find it plenty comfortable to use, and so does my wife, and we're at opposite ends of the human size distribution. I don't really use it lying down like I used to do with my PSP, but that's not much of a loss to my mind considering how much more advanced games I can play with it on the go.

I'm a bit bummed that I haven't been able to find a good factorio-ish building/optimization game for it that actually works well without mouse+keyboard, but I'm sure one will show up eventually. I haven't really experimented with an external monitor+mouse+keyboard with it as I'd just switch to the computer at that point.

All in all super happy with it, it does what it's designed to do incredibly well.