The main disadvantage of PC ultrabooks - Windows 8.1....period. It's "Let'sCallItModernNotMetro" interface is a mess. Windows 10 looks promising, but then again...it's still Windows.
Reducing an OS to something that's blown out of proportions and (to some extent) has been already fixed? Check.
At the end of the day, the call is whether your apps work or not; the OS and its desktop is not something one spends his entire day staring at.
OSX, especially Yosemite, has its quirks too (caveat: I'm not very fond of Yosemite and some of its annoying bugs).
If you have iOS devices, especially an iPhone, iCloud and Continuity and Handoff are great features; if you use Android tho, they'll mean nothing to you and you're better off relying on Google service integration (which works great regardless of the desktop OS you use).