Very interesting--I'm a journalist and headed in the same direction. The factors for me: I hate glossy screens, and Apple won't provide a matte screen for its iMacs or 13" laptops. This is sheer stubbornness, a case of Jobs deciding what's good for us. (He loves glossy, but it's not a coincidence that business machines all use matte. They're better for doing real work on, as opposed to consuming media. I realize opinions may vary, but that's what choice is about.) The hardware more generally: the aluminum keyboard makes my hands ache, so I use Logitech--so why pay for the trendy design if I'm not using it? I don't particularly like the idea of all-in-one computers, yet that's your only option for a non-economy/non-stratospherically priced mac. Again, lack of choice.

And, of course, price. I want to have a desktop and a laptop, synced. With Apple, there's no way to do that for under $2,200 (low-end iMac plus Macbook)--unless, as I do, you use Windows for your second machine. Then you've got extra software costs (two copies of Office) and syncing headaches.

I'm leery of losing things like Expose and Time Machine, and I love the software that Apple developers create--but hardware choice and price are going to win out. Plus, as you've noted, there are some bonuses like OneNote.