Mine was $1! I love it. I just bought a wireless mouse and keyboard for it, because it's honestly just a great way to stream stuff. Now my computer can be in my living room, and my office at the same time!
You can do both. The default is Big Picture mode, but you can back out if it and get a desktop.
But, you'll basically have to be a foot or two from the PC to read anything unless you have a desktop environment set up for a large screen (KDE plasma has a TV version)
Can control it in general, but the first few times you'll have to run over and look at the monitor to do stuff.
It generally assumes it's being used "close" to the computer, so instead of complex pairing, it just shows a code on one you type into the other.
Sometimes windows will get antsy and pop up a dialogue that can only be interacted with locally, but it's only one or twice ever.
I remember that sale and annoyed I didn't buy one. At the time I thought I'd never use it. Fast forward a few years and I occasionally use Steam Link on a Raspberry Pi, so I would have used it. Oh well.
Think about it though. Probably some overlap with the deck. And hiring one dev very part time to keep this thing alive is nothing for them. Which makes the steam deck way more lucrative
Flat structure. If you want to work on something, work on it; if it's not interesting to you, find something else. If you have an idea find people that also seem passionate for it and start making it, if you can't find people then ¯\_(ツ)_/¯
It's why valve rarely makes anything, but when they do it's super high quality