Top paragraph is how FF5/XP renders locally installed Droid Sans (TTF). Bottom paragraph is how the same combination renders @font-face version courtesy of FontSquirrel's webfont kit generator.
If I understand correctly, latter is .woff, but if I change @font-face statement to reference .ttf only, I am still getting the same appearance. Moreover, Google Fonts serves .woff as well and it looks like the top version. The same goes for WebType.
Any thoughts as to why this could be happening?