As the title suggests, this will be a very nice feature, being able to sort my songs by the new difficulty system and would make searching songs much easier. The difficulty system being this for example, http://osu.ppy.sh/s/153614 "star difficulty: 3.48" for this map. Being able to find songs in the 3.0-3.3 difficulty within the 1300 beat maps I have would be very convenient and I think this stands true for other players as well.