There is nothing better than Smiles. For several reasons:
1. They are a clear indication that things are going well.
2. Try to be angry and smile.  Just by forcing yourself to smile for awhile you disposition will change.
3. Its another way that you communicate with us.  I love seeing you begin to figure out your facial expressions (beyond pissed off and asleep :P).

I got my first smile from you yesterday.  Maybe it was a fluke, maybe not.  I don’t think so.  You were happy, fed, clean, and doing leg squats on my lap looking at me.  Then you smiled, Amazing.

Keep the positive reinforcement coming please!