If im not mistaken, OSX uses a different font smoothing technique than XP/Vista. I recall noticing a slight difference when I first got my Mac Mini. I wouldn't say it looked less sharp per say, I just noticed that it looked different. Other than that, as long as your resolution is set properly, there's not much else I think you can change to sharpen it up (AFAIK).
That being said, there are LCD sample variations, and it is possible that yours looks different from how it should. Have you looked at other MBP's in person and noticed the same? My Macbook is sharp as a tack, but I noticed my dad's looks a bit softer.