Just thinking about general use personal computers (not remote boxes, servers, etc.), the only thing I feel like Linux adds to the OS X experience is tiling window managers.
But I only care about them on my giant 4K screen at home, where I only /need/ to use OS X for certain non-linux apps and where similar functionality comes from 3rd party apps. On my laptop(s), I tend to full-screen basically everything anyway, which works about the same on every system.
So, desktop PCs....no. You can build something better than any company can offer for similar or less money and with the compromises you want instead of the ones someone else decided on.
And for laptops, no. I find that I can get what I want from products that are already on the market. I /would/ pay for an Apple Laptop with a 12" 16:10 very high resolution screen and a trackpoint without thinking, though.
Interesting....