Psst! Here's a secret tip: You can skip to the next song just by swiping the album cover.

Like its web-based counterpart, the Slacker Radio app brings mountains of streaming-music goodness to your iPhone or iPod touch. You can create a personalized station on the fly, browse a selection of popular and spotlight stations, or choose from around 15 genres--everything from Alternative to Youth. Sick of music? Check out Slacker's killer Comedy station, which rivals anything you'll hear on XM Radio.

The attractive, smartly designed interface devotes almost the full screen to album art, but it still manages to leave room for song info and playback controls. You can tap the "heart" button to mark the currently playing track as a favorite, or "ban" to keep it from playing on that station again. A tap of Now Playing takes you to a station-info screen, where you can fine-tune your artist selections (such as add or remove favorites). Tapping the song name leads to an album review, information about the artist, and a "Buy on iTunes" button.

As expected, Slacker sounds fantastic over a Wi-Fi connection. Unexpectedly, it sounds nearly as good over 3G and even EDGE. You do have to sit through the occasional commercial, unless you have a Plus account ($3.99 monthly), which also entitles you to unlimited song-skipping. (Free account holders can skip only six times per session with a particular station, though it's easy enough to get around that; just switch to another station and then back again.)

Slacker's only real shortcoming is that it lacks a song buffer, meaning you can't listen offline. Everything runs live through the Internet. The company's portable player offers that capability, as does the just-released BlackBerry version of the app.

Even without offline listening, Slacker hits nothing but high notes. It's a must-have app for music fans, especially those who like to discover new music.