Five Steps from Mac to MS? Bah. Are we really back to "Mac vs PC" time again? For the love of baud, own both.
No really valid arguments.
Yeah, hardware-wise, Macs are arguably more expensive - but take into account software and it evens out pretty fast...most all the software you need on a Mac is cheap or free.
Upgradability? Don't buy a flipping laptop and then complain that they're too hard to upgrade. With the exception of hardcore gear geeks, most laptops are a pain in the ass to upgrade beyond memory.
No ergonomic keyboard? It's a laptop.
Games. Yeah - Steve Jobs hates games. This doesn't really belong in a list of reasons to change from a Mac to a PC - if you want to play a lot of games well on your ONE machine, then just say "I'm getting a Windows machine so I can play games" and stop with the silly lists.
And Scrivener. Scrivener alone is enough of a reason to own a Mac if you're a writer. Yeah, there's a beta for Windows. Meh. Scrivener belongs on a Mac.