Interesting that you ask about this - I've just started looking into these myself for a mainstream project I've been working on. Been fiddling with the CSS hacks they have posted over at
http://css-discuss.incutio.com/?page=CssHack - and being a web standards purist, I've also been reading the discussion over at To Hack or Not to Hack (
http://css-discuss.incutio.com/?page=ToHackOrNotToHack). As for the debate - I can see both sides. As a web designer/developer it's frustrating as hell to see good CSS go bad because of IE and other browsers that refuse to become compliant - but also, in support of W3C, I hate hacking anything - I want to be 100% compliant myself.
Damned if you do... damned if you don't.
Little plug - check out Klixxx Magazine for lots of CSS tips and tricks. We've had a lot of special features on this subject and I know that our editor has some more planned for the future.
Hope this helps get you on the path you're looking for!
