Bit of a lengthy one but I put SteamOS on a dual boot recently. It wasn’t a total disaster just a headscratcher ..
firstly my experience was the exact same as yours down to the calculator shortcut lol
most keyboard shortcuts ( back space, escape in certain menus ) don’t work depending on where you are in the client. In fact I had to use the controller to exit menus even though the keyboard and mouse were plugged in, even the steam icon to main menu button didnt work i had to use the 360 controller home button !
Then there were typical learning curves which took some time and frustration to get things right, like the downloads menu and the downloads pause and que menu.
But worst of all as confirmed by Valve SteamOS doesnt support any higher resolution at the moment than 1080p .. that makes the UI blurry on a higher resolution screen.
Even in game the resolution menus don’t work so I couldn’t higher than 1080p on SteamOS , not a lot of people know that but valve are working to fix that in a beta update I believe and it will require a forced to 4k resolution command to be entered AFAIK so not for every day users ( which was kind of the point wasn’t it ? )
Other than that often vsync worked well but was not able to be defeated in menu's where by on the desktop client you can .. which helps for a lot of games that run smoother at really high FPS unlocked (not to mention thats higher refresh out of the window )
In the end a nice install of Ubuntu Gnome / Mint / Arch Linux with any number of possible alternatives:
Big picture on steam start with startup application being steam
Login option for Big Picture mode on Linux login menu
Manual launch using the desktop steam controller driver as a mouse
Hi-DPI selected on Linux desktop with game icons as launchers
Real deal steamOS installation as Login option ( yes thats possible )
I just lose so much of what I can do on my desktop.
Other than that .. The browser is TOO scaled in , like its 250% equivalent zoom and too much even for a 10foot interface. I can add Firefox / Opera to Big Picture as a launcher on Linux and it seamlessly ( and nicely animated ) full screens firefox back on the desktop to browse ( with script blocking, cookie blocking and all those addons and bookmarks etc.. ) until I close and then really smartly it goes back to Big picture and doesn’t get stuck on the desktop, which is pretty much better than SteamOS will ever be able to muster.
In many real tangible ways Big Picture is better than SteamOS Big Picture, which is just a way of making the migration to a Linux ecosystem easier for new users IMO.
Still I do think running Linux with Steam is better than Windows with Steam for a HTPC ( for me anyway ) because Linux is more akin to a console OS in that its processes sit quietly in the background, there is no firewall pop ups or virus checkers, malware stuff, endless menus and updates with auto reboots (like win 10 ) it can be built with a minimal install, boot in 2secs and sit there just letting Big Picture get on with what it wants to do in absolute silence using less than 250mb of RAM but still be a full desktop OS with all the stuff you need.
Im not sure valve would even endorse Debian SteamOS over someone with the ability to setup a Debian Linux+Steam Big Picture system with some custom controller button mappings for desktop navigation from the couch.
Ironically the more Dev's that make games for SteamOS the more those menus that take you from the UI to the desktop will be phased out.