I really like age four. Will has quite an independent streak at this age. For instance, he can go to the bathroom by himself. On weekend mornings, he can entertain himself for a bit, turn on the TV and let Mom and Dad sleep in a little bit. When Joey is ready to come inside sometimes, he can open the door and let him in. He's creative, talkative, and has quite an imagination.
But the best part of age four? He can pick out his own clothes and dress himself. No longer does he have to wait for one of us to say "time to get dressed!" and pick out his clothes for him. :)