I discovered that on large/huge fonts ClearType does have a negative impact. Just take a look at http://patterns.dataincubator.org/book/ page (check title with huge fonts versus normal text). If you are on Windows 7 you can use Win+Plus/Minus to zoom in/out.
I'm looking for a configuration that would make both small fonts and large fonts look well. The system is Windows 7 but I suppose you could replicate the problem on Vista and even XP if you activate ClearType.
- ClearType on and tunned - small fonts looking good and large one looking bad
- ClearType off - small fonts looking bad and large one looking ok (smoothed)
Just for fun I observed that there is way to activate OS X like font rendering on Windows but they are too smooth.