Cleartype wreaks havoc on webfonts. Turning it off gives you smooth fonts, but jaggy regular text >:|

Strangely IE6 (and 7? i think) are OK even with cleartype on.

There is a css hack to get font smoothing on windows:

h1{ text-shadow: 0 0 0 rgba(0,0,0,0.0001); /* Transparent Shadow make some kind of webkit font smoothing kick in */ }