Why I switched, and ease of switching to outlook.com
I switched to outlook.com only because I use Outlook 2010 (the real one). It is a shocking change, and perhaps too plain, but I kept it. Granted, I do not use it often due to owning Outlook 2010, as I've mentioned.
Didn't have to change a thing on Outlook 2010, it still syncs flawlessly with it. When I go to my hotmail, it automatically signs in to outlook.com, as I had it set up to do in hotmail.
More on Outlook 2010 and 2013 comparisons
I should also note that I do not plan to pay extra to 'upgrade' to outlook 2013. The appearance is far too 'white', but I'm sure the functionality has improved, if but slightly. I am playing around with the 2013 preview at the moment on another computer in order to compare. The reason I bring this up is because outlook.com was based off of outlook 2013.
Descriptions of outlook.com
Basically, this hotmail -> outlook is outlook 2013 with less functionality. Hotmail appears to be more user friendly (perhaps because I am used to it?). Some people enjoy the 'simplicity' of this basic outlook.com provider.
Grade sheet
I'd give outlook.com a B- score. Hotmail would get a B+. Outlook 2010 gets an A, and Outlook 2013 gets a B+
And here I thought they were expanding hotmail into one big giant email provider/calendar/everything location. Seems they are scaling back?