You can always play around with font smoothing in the appearance pane in System prefences and use light for an xp look; but try to use automatic, (default), for a couple of days to get used to it. It will appear best after some good use with it this way.
Yeah, it will appear best as soon as you get glasses because of blurynes.
The blur problem is annoying if you have 10 pt letters or especially smaller. That is quite problematic, if you are using a 20" or bigger screen with 1600x1200 and up resolution.
But if you turn of anti-aliasing in OSX, what will you get? Gosh.
Windows's ClearType is much better for screen reading, especially for small typeletters. You know, there must be made a difference bettwen the screen-reading and printed material-readings. Simplay because printer materials is still much sharper.
When (if) we get high dpi resoultion monitors (like, let's say 150-200 or even more dpi) in the future, than Apple's font antialiasing will be the one, that can be used for reading and elegantly displayed on these screens. But today, it will help you, that you get glasses, if you don't have already.
Linux has also better font anti-aliasing than Mac OS X.