I use Windows as desktop OS, Xbox for gaming, Android on devices and Linux on server (and some desktop Linux too, mostly on a netbook as a writing environment, and in VirtualBox on the more powerful Windows laptop for random Linux-y things). Most of the apps I use regularly in Windows are open source, however, and have Linux ports.
Overall, I like Windows 10, aside of small instability due to very minor driver issues (not bluescreened in a while though, and I hope it's a good sign).
The only massive gripe I have is that the photo app is a bit slow and silly. Look, I'm a serious amateur photographer, and I'm constantly amazed by how bloody difficult it seems for folks to make a photo management software. Basically, the only solution that actually works for me is to stick the photos on a NAS and tell the application (read: digiKam, which isn't my first choice, but seems to be the only one so far that actually works in even remotely sane manner) to store every bloody detail on Exif/XMP/what-have-you. Because I guarantee that the nice "simple" photo management app you have at hand will try to store everything in a separate database that gets corrupted randomly or evaporates during upgrades (adn tehn u ar lik "omg where did my photo captons go oh nose"). Oh, and it absolutely insists that the image collection is stored at a very specific directory on your local hard drive. Or it makes an assumption that every single image file in your home directory is a photograph. Case in point, Windows 10 photo app first made the assumption that everything in Pictures folder is a photo, which is silly because I also draw and stuff, and applications tend to store image files there (I seriously thought the Windows 10 start menu tiles were showing some stock photos or something, until I realised my music player was caching artist and album images in Pictures folder). I could change the photo storage locations, and sometimes Windows even recognised that fact (it still kept adding random pics and I have no bloody idea how to remove them from the photo library. Gah!
In short, I have no need for this particular photo manager because these photo managers don't fit my workflow. Which wasn't a problem in the past, because even if this kind of apps would ship with OSes I could simply choose not to use it. In Windows 10, they made things worse by integrating the image viewer and the photo manager. I'm seriously considering installing an alternative image viewer to do a thing the basic operating system tools fail to do. (Ah, back to the happy days of Windows 3.1 - not...)
Oh and irony and ironies, while writing this post, I can't even experiment with the app or probe the settings because the application straight up refuses to start for some reason.
Also there are small gripes that I have. There's been a whole lot of cool things here that I had in Linux ages ago (multiple desktops, woot - welcome to 1996, Windows!) but if I wanted one new feature in Windows, it'd be some kind of a sane update to Explorer to take advantage of all the cool stuff in file management that we've seen in, uh, last 10 years in other operating systems. (Just adding multiple tabs or panes would make stuff so much better, and it's kind of annoying that all of the third-party Explorer replacements are terrible too...) Just copying OS X 10.3 Finder to Windows Vista and then going resting on your laurels doesn't cut it, Microsoft...
Oh, and the network drive access usability sucks too. Can I get some nicer bookmarks/shortcuts to CIFS drives? (There's probably power-user methods for these, but the user interface as it is is pretty cryptic.) Windows invented the damn CIFS thing, why is it so difficult to use it?