The unsportsmanlike conduct penalty he has already picked up for taunting would suggest that he's still immature and undisciplined.
Somebody also mentioned on twitter that he may have removed the NCAA decal from his helmet before the game? I haven't paid close enough attention to know if that's true or not, though...
Manzel has the potential to make Jeff George look like a choir boy. Baring a huge implosion prior, some NFL team is going to draft him for his name. Should be interesting to see how his attitude goes over with veteran pros.