Sometimes I like to go back and play old stuff too.
I do not see a performance penalty at all with WINE. Most games that work play at speeds matching or better than windows. WoW is usually a big example of that, as are emulators.
Running either in wine is a fine benchmark on performance.
Now, this isn't to say that Wine is totally up to par with Windows in terms of compatibility, but performance hasn't been a significant issue for quite some time.
This might be enough of a barrier to stop me using it right now.
I initially had that problem, but it seemed to be the fact that (on top of some phoning-home options that I missed disabling originally, which seemed to play some role in the slowness -- disabling them helped) the Windows 10 update from Windows 8.1 also, for some unknown reason, rolled WLAN drivers back to the versions that were several years old (pre-Win8.1 at least) and fairly broken and couldn't automatically locate new ones; redownloading the latest (for Win8.1 -- no Win 10 specific drivers were available for the hardware in question) drivers (which is what had been installed prior to the update) resolved the slowness problems.
Steam OS is a Linux-based OS designed primarily for gaming. Any and all cloud-integration will be specifically gaming-focused.
Can you not see the difference between that and a general purpose OS like Windows harvesting data everything you do on your system?
I won't be using Steam OS to do anything very sensitive like sending or receiving personal e-mails, editing word documents or spreadsheets, or browsing the internet for whatever reason.
Unless you consider firing up a shooter or a city-building sim sensitive.
The two OS's have very different purposes and use-cases.
There's a big difference between 'allowing' and 'requiring'.