Almost forgot but I ended up trying out a total of 16 demos ("or more" according to the badge) with a few more installed, which I assume I still have access to:
Fabular: Once upon a Spacetime Demo: Nope. I really like the concept, the art, presentation, etc. All top notch but I didn't realize there was
so much faffing about. Maybe this will be one I'll revisit for the 1.0 version but I really wasn't in the mood for a dialogue heavy, almost Visual Novelesque shenanigans and inventory management. Maybe some other time.
Dome Keeper: This was super interesting and intuitive to play. You basically just mine resources (manually) to upgrade your dome to fend off alien attacks. Real straight forward concept but very addictive. I would've played more but would rather save my playtime for the full game. Definitely glad I tried it out as it made a really good first impression.
Selaco: Need I say more? Utterly fantastic in every way possible. I could wax lyrical about it for ages but all I will say is that even if you're a casual fan of FPS games you owe it to yourself to give it a whirl. It's DOOM meets FEAR meets Metroid Prime meets Duke Nukem (in terms of interactivity with the level props). Loved it.
Nine Sols: Defaulted to Chinese language so I had no clue how to change it. Played it for a bit and didn't seem half bad. However unless it comes out to raving reviews I'd rather just play Ori or any of many other stylized metroidvanias I still have in my backlog.
Alina of the Arena: Sometimes when you see a game on Steam, watch the trailer, check out the screenshots, etc it can look appealing. But then when you actually play it for yourself and see the game running natively it leaves a bad taste in your mouth. This was such a game for me. Presentation ended up as rather poor and the gameplay itself didn't really do anything for me either. Once again I'll just stick to Monster Train, Sly the Spire, Phobies, etc.