Sona is my main support, Her spells are very short cooldown, meaning you can make alot of use of her passive to harrass in lane very easily, leaving your AD free to last hit uncontested, and eventually set up an easy kill, her Ult can vastly turn a teamfight, i have played a Sona/Kog'maw lane and in a 2v5 gank, managed to get kog a pentakill (i did record it, link if you want to watch http://www.youtube.com/watch?v=ns4Sz...gkujPHS4f4BOg=). Her heals aren't extremely powerful, but are significant enough to keep an ally alive, and the cooldown is short enough to use it repeatedly. Her E is a nice spell even though it's not a huge speed bonus, it can make chasing/escaping alot easier, particularly when combined with Shurelia's reverie.