Microsoft, can you please tell me why you felt it was necessary to change the default line spacing to 10 pts. after a line? The default should be 0 pts., and if a user wants to change it, they can change it. I have to teach my students how to make this change every time they write a paper. Now that we are standardizing Word 2010 at my school, I can see I will need to help faculty and staff change this default, too. I cannot think of a single defensible reason for monkeying with this particular default feature, which prior to Word 2007, was always 0 pts.
Correct formatting for MLA (and every other style I can think of) calls for double-spaced line-spacing, and this setting you changed introduces extra space after each paragraph. You have introduced incorrect formatting by default and have forced users to change this default in order to correctly format their writing. That is not user-friendly, and it is not cool.
Also, I hate Calibri.