One advantage for Microsoft is that the Linux desktop environments currently also mess around with their UIs. Maybe in the long run it may turn out well but currently Gnome Shell and Unity make life hard for people who just want to use Facebook.
I have personally not formed any opinion if Unity and Gnome Shell are good or not. I have used them too little to say, I primarily use XFCE myself which was very easy to get started with.
How? I installed Ubuntu on an old laptop for my wife and she finds it as easy as ever to do email and Facebook because essentially the only app she ever runs is Chrome and it's locked in the Launcher. She doesn't even know that Unity exists so it's certainly not making life hard for her.
My normal environment is OS X, and I've grown used to using Spotlight to start apps. Cmd-Space + a few keystrokes, hit Enter. The only time I use the Dock is to resurrect the occasional hidden window. I'm too lazy to bother configuring the Dock. Start menus, even gorgeous ones like the OS X Dock, are so 1999.
Similarly, when I browse the web, I rely on keystroke completion and search, not on bookmarks. I'm too lazy to maintain my bookmarks
That is great when you know what you are looking for... but when the image editor is called GIMP, or KRITA, the audio player is called rythmbox, the video player is called VLC, then you need to know those names in order to find what you are looking for.
IIRC common users went to Windows running from having to remember MSDOS commands.
I find this to be a nice feature. I am a developer but don't have the time to tinker with every little on my desktop. For me, and with the newest version of unity, it works well enough to let me get on with my work.
And when I just want to create a spreadsheet, I have to know the app is named Excel, or when I want to play a game I have to type steam.