ClearType font rendering is not so good, especially if you are using an high-dpi lcd screen.. it has a bad forced hinting that deforms the original font.
I suggest you to try another font renderer like this: https://code.google.com/p/mactype/
it uses the same renderer built in Linux and Mac, after you configure it as you like all your fonts (in GDI applications) will be rendered in a more correct and readable way, Ubuntu font also.. I'm using it on Windows with a fullhd laptop display, the difference is noticeable (Ubuntu font is rendered perfectly in Sublime with it, but eg. also microsoft Consolas font is more beatiful..)
PS: do not enable DirectWrite in Sublime configuration if you want to use MacType or you'll have the same font rendering of Internet Explorer, Visual Studio, etc.