The biggest benefits are going to be the identical UI. MS has done a superb job making the UI for Windows 8, Windows Phone 8, and even XBOX damn near identical. What's great about this is you can set up your information that matters to you to display the same way, at the same time, on every device. You hear a lot of "ecosystem" jargon being thrown around on Apple forums. I think we are going to see a lot more of that sort of discussion here too, especially with skydrive. The beauty of developing for any of the aforementioned OS's is that you develop for one, you develop for all. We are going to see a lot of cross compatible software popping up here. One such (simple) example is Microsoft's own One-note, which is a lot like Apple's reminders, if you are familiar with that. I can set notes, make shopping lists, and it seamlessly bounces between my phone, PC, and (soon to be made by the elves) surface. It's honestly everything I have enjoyed from Apple (and I am typing this on an iMac with an iPhone 4S to my left) but coming from Microsoft with a UI tailor built to match between devices.
As a bit of a side-note, my wife is a huge Apple fan (I'll be honest, I become one as well since the advent of the iPhone. She was a bit apprehensive of me getting a Windows phone 8 device, especially with how lackluster WP7 really was. Seeing me use Windows 8 and going back to WP8 really has her thinking about a windows phone (she has an iPhone now). I think it would be an easier sell if our iMac had touchscreen capabilities. Using the mouse for a lot of things in Windows 8 is a bit counter intuitive, or at least it feels that way. Being able to use your finger right on the screen makes a world of difference.