I’m working on a site design and I’m using Google Fonts, the “Raleway” one particularly. This font is characterised by it’s thin lines, and it’s being rendered well by all browsers, except under Windows 7 Safari it looks like it’s rendered bold, or at least it’s really awful looking.

Is this a Safari issue? Or a Google font issue?
I often find the opposite problem, fonts that appear slim and stylish in Safari , appear TOO slim in Windows browsers to the point where some strokes almost disappear.
It’s to do with the different methods of font rendering … Windows chooses to constrain fonts within pixels producing a somewhat sharper image but affecting the shape of the letters so that they do not necessarily hold true to the way the designer originaly meant them to look, Apple on the other hand use a rendering system that interpolates half-pixels producing a sometimes softer/fuzzier appearance but which holds truer to the letter-shapes intended by the font’s designer.
Neither system is perfect, both have their fans and their haters, I can see merits in both systems and I can understand the decision process that has led them to choose the two different methods, so I wouldn’t describe either of them as “crappy” but it does make font-choice difficult when trying to design something that will appear somewhere similar on both systems.