Leaks, unfortunately, isn't perfect and may present false positives. My understanding is that this is especially true if you do any threading in your code. Due to the nature of how threads and their memory are handled, Leaks may think that an object was leaked when in fact it was properly taken care of (I know I ran into this in my newest app)
In other words, Leaks is great to catch some stuff, but there's no replacement for the human touch