I like the way it does "find on page" - you type in a little box at the bottom and it highlights what you are looking for. Tabbed browsing is good, but I think Safari does that anyway. The RSS (really simple syndication) feature is great. If you are on a site that supports RSS, like BBC News, a little orange icon comes up bottom right. If you click it you get a special type of folder-style bookmark in your bookmarks / favourites. When you click that later, it fires out to the right a list of the latest headlines and you can just choose the one you want without having to go to the bbc news front page, or go anyhwere if there's nothing you want to read. It's good for keeping up.
I've never really used Safari much so I don't know if it's worth switching from that. I'm fairly new to macs. The ones at work have IE on them. When I got my own I put firefox on it straight away.