@jamie:

Post a screenshot of C9, MSN, and Desktop side-by-side.

As for IE setting, you have TWO places to set.

  1. Font size.
  2. Zoom.

As for system wide font size, including Desktop, Visual Studios, and Windows Explore, change DPI in control panel. I used to set 125% on my 24in 1080p monitor. Once I get to 27in 1080p, I get my DPI down to 110%.

And if you are using MetroIE in CP build, MetroIE is not as smart, it doesn't default your zoom to match your DPI. You need to zoom manually.