If you read your RSS feeds in more than one place (that is, if you want to read them at home, at work, or on different devices), you'll want to try a web-based RSS reader, similar to what Google Reader is now. NetVibes (pictured above) is one of the most popular web reader, offering a Google Reader-like interface as well as a snazzy iGoogle-like homepage.
NewsBlur is also a great option, with an interface that's very similar to Google Reader (and arguably a little more polished). You create an account with them, subscribe to your favorite sites, and can read them on any computer. They even have Android and iOS apps that'll sync your feeds, too.
Feedly is popular, but definitely different than Google Reader. Its interface is less traditional and a bit more "newspaper-like," but it's very pretty. You need to download a browser extension for Chrome or Firefox to use it, but you'll be able to sync your feeds between browsers and even to Feedly's mobile apps. Update: Feedly has also said that they'll have a "seamless" transition method in place when Reader goes down.
My criteria are that it be fast, Safari for Mac compatible, and have an iOS app. Thoughts?