We've tested a few menubar music remotes in the past, and there's not that much difference among them. What makes Skip Tunes different is its simplicity. It operates on the minimalist principle. It controls iTunes, Spotify or Rdio.
Instead of getting a lengthy menu like with some apps, Skip Tunes displays the album cover, what song is playing, and controls. That's it. The controls are the same that you get on the stock Apple keyboard, but it looks good. That's enough to satisfy those who go for the smaller visual footprints. It's a great way to see what song/album is currently playing without having to go back into an app, and you can toggle the ability to see the controls in the menubar. It's one of those apps that you wish would be a part of OS X by default. Looping in Rdio and Spotify is an added bonus.
Some users reported that the app stopped working with Rdio after a few minutes, but I'm not having that issue. Skip Tunes can't auto-detect what player you have on. I had Rdio on when I launched the app and had to switch the default player to Rdio before it latched onto it.
Update: I have started to get the issue with Rdio others have reported, but it took going out of the program and coming back.
Skip Tunes is 99 cents on the Mac App Store. Other apps have more features, but the simplicity has earned Skip Tunes a permanent place in my menubar.