In Oblivion, I had the problem of completing the main quest and guilds by level 12-15 because I would level as efficiently as possible... but in Skyrim, I don't have to worry about that! I am level 14 and I (assume) am about to complete the main quest. I have done nothing else!

EDIT: Though, I do have one small issue with the game. I have more souls that I know what to do with.... it would be a good idea if you could use them to reduce shout recharge times.