I'm not trying to argue at all here, but how exactly does it have "Microsoft's signature on it in more than one way?"
Secondly, AMD CPUs (as well as intel 64 bit) are working but not Video Cards at the moment, at least not in a non complicated way.
I doubt that what you say about using Swap for "nefarious" purposes is correct, as you might know,
"It is normal for Linux systems to use some swap even if there is still RAM free. The Linux kernel will move to swap memory pages that are very seldom used (e.g., the getty
instances when you only use X11, and some other inactive daemon)."
I know that getty and X11 might not be used in SteamOS, but it works the same way.
I give you the Windows filesystems part. I don't know why they decided to use that maybe it's because of the usability. Windows is EVERYWHERE like it or not, Maybe they thought, hmm... we should at least in some way make this usable with Windows. Maybe when dual boot is allowed Steam on Windows can use games from Steam OS (don't quote me, i have nooo idea)
People have to understand that in a corporate setting, you have to sacrifice certain parts of open source. I know that sounds horrendous, but it's true. Google doesn't release ALL their code for ALL their products! Most open source packages are freely distributable and freely editable, which means that they aren't under any obligation to make anything work with anything other than SteamOS.
I don't see how it looks like it was made by amateurs, no offense. People LOVE big picture mode (obviously some people don't but that's life, we all have opinions!)
All in all, just remember SteamOS is in beta, I'm sure by the time it's freely available it will be great, will play nice with all drivers, and will work out of the box. Again, I'm not tryna flame or anything, just thought I'd put in my opinion.