tagging in Mail and smart folders in Tiger

[buckuxc]

I just signed up for a gmail account recently and I'm really tempted to use it instead of mail.app (or at the least, use mail as an imap server). One of the things that interests me in gmail is the use of tags (I assume it's like flickr and deli.ciou.us). This really makes email searching so much easier and doesn't require one to figure out a system of folders first. Looking at the new mail stuff at the Tiger page, the Smart Folders thing looks promising, but will it have the ability to tag emails just as you want to tag them? How exactly does it work and how good?