It is hard to find something to complain about! This app just works, and does it intuitively. What I want to do is right there, all the time. The interface is elegant but doesnt get in the way at all.
You get this app to convert units - and it does. Pretty much no mater what the type of conversion it is, itll be there, with the ability to convert it to many alternate units.
I love it, have had it for several years, and use it at least once a week - sometimes on the iPad, sometimes on the iPhone.
My only regret is that there doesnt seem to be anything this elegant and functional on the Mac!