I've just submitted a new version of mScrob to the app store.  This is a free version, but has ads.  Other than that there are no restrictions.  It's optimised for iPhone 5.  I've done this as there is now an official Last.Fm app.  I used it for a bit, but went back to mScrob, as I prefer the built in music player - with the official app you have to use the Last.fm app to play music, and it's too busy for me.

Income from iAds is tiny for the amount of downloads something like mScrob gets though.

This is the first non-Cocos2d app I've updated for iPhone 5, and I have to say it was incredibly easy! I justed added the extra Default.png, and the interface pretty much adjusted itself - I just need to make a couple of changed to some of the graphics and that was it - job done.  It's amazing how much easier things are now that in the Xcode 3 days!