What's great about SweetFM is that you can control it with an Apple Remote or the Mac's media keys, it has unlimited song skipping, you can export tracks to iTunes playlists, see the next 4 tracks coming down the pipe and pull down album art from Amazon or Last.FM. It's actually something of an interesting argument for native apps over web apps, even for actual web services—I like its user interface way better than the running Last.FM in my browser, and I feel like I have way more power at my fingertips.
To the point about streaming vs. file sharing, services like Last.fm, Pandora and Slacker have gotten to the point that it's easier and faster to find new music using them than poring over torrent sites. Or something like that. SweetFM is slicker, anyway. Do you guys actually download less now? [Chocomoko via TUAW]