If I didn't trade number three, I probably would've picked Chriss. I think that kid is going to be something special, or at least could be if developed properly.
I like the "if developed properly". That way, if you are wrong in your evaluation, you can blame how they developed him.
Or this could just be a Celtics fan's evaluation who has watched our number six pick from 2014 not being developed properly by largely being played out of position/role... 
I think Smart is being developed very properly. He's an emotional player, and he's put in positions where that energy is more easily channeled into a positive (showing no fear in any defensive matchup) than a negative (playing PG and resorting to hero ball). I think we'll see more ball-handling roles given to him in the future, when he's ready. Stevens has a huge amount of trust in him, and with IT gone, he should get ample chances to run the second unit.
I disagree, at least offensively. He's clearly been at his best as a primary ball-handler, yet he played last year almost exclusively with Turner and/or Rozier as a spot-up shooter off the ball. Now, since he's had less offensive responsibilities, as you pointed out he has been well developed and utilized as a primary defensive option. However, that's not really the part of his game that needed much development; it's his offensive game that he needs more reps, especially as the primary ball-handler, or at least in a co-ball-handler situation.