1.) Laptop hardware/construction that rivals Apples. I hate plastic. I hate it.
2.) A usable trackpad. Apple has by far the most usable trackpad and it works well. Windows/Linux laptops force me to bring a mouse because the trackpads/drivers are essentially crap by comparison.
3.) Hassle-free wireless and graphics card drivers. Linux I'm staring you in the eye poking you in the kidney. This isn't always a crapshoot, but boy howdy can it be.
4.) An supported upgrade path. Too many "PC" manufacturers put their hardware out to pasture the day it's released. No updates. No support.
Windows is largely unusable for me for development work[1]. Babun or cygwin make things better but I hate having this fucked off environments disconnected from the core of the operating system. It's like working/developing in a vagrant box without wanting to...
Linux is damn close but without a good hardware vendor it's a no go. I could buy a Mac and install Linux on it, but what's the point? Might as well just use OS X... and here we are.
[1] I want to emphasize the "for me" part. I'm not trying to say you can't enjoy it, or that it's across the board "shitty" by any means. I gladly recognize for some folks-- it's wonderful.