^ S-pen and digitizer which changes a lot if you want to do any kind of drawing or writing. That's all. For some people that's worth the money, for some it's not.
Anyways I bought myself a Windows tablet (The Asus T100) and I sold my Macbook Air. I loved it, but it wasn't useful to me since I have a PC with big screen and all that at home and I also have a company laptop, so the MBA was wasted on me.
I will probably sell my 2012 Nexus 7 as well or just keep it for playing with new Android releases and stuff.
Windows 8.1 is not ideal but it gives me lots of functionality that can't be matched by Android or iOS, even if it's far less convenient especially to use on the run.