phroggonalog
Dalayan Master
55 is also a good time to finish/start some of the longer quest lines. I usually wait till 55 to start MQ on my characters and usually good for getting through the first dozen AAs or so depending on how much time I spend in UC (Which is good XP at 55). You can start the Vah, faction, and diety quest lines.
This is very true whether or not you are a fan of the 50's (i hate them)