About using CSS hacks
The other day I posted my thoughts on the use of CSS hacks in Stop using CSS hacks now. I rarely use CSS hacks, so I was a bit surprised to see so many people defend them.
Anyway, I do agree that whichever method you use to send different CSS rules to Internet Explorer you'll have to be prepared to change some things when IE7 is finally released. Eric Meyer has written a couple of posts on the pointlessness of doing anything now: IE7 and IE7 and To Hack With It. Jonathan Snook has similar feelings: IE7 and the use of CSS Hacks. Both of them make good points.
So the conclusion is that whether you use CSS hacks, conditional comments, or neither, you will need to check if your sites are still OK when Internet Explorer 7 is released.