I think there's real potential to take on SongPop. SongPop's interface needs work, and SongPop doesn't really feel as responsive as a native app, since it kind of isn't - it's Flash compiled to native with Adobe AIR.
we had a great experience using xcode with MakeGamesWith.Us rather than non objective-c languages that SongPop used! They are great people to work with and we've learned so much!