As seems to always be the case, I'm seeing all of the Marcus Smart arguments fall on either one or the other extreme. Everybody either loves him way more then he deserves, or hates him way more then he deserves.
The reality is that Smart has both sides to him.
On one side of things Smart is fearless, he's tough, he's a tireless worker, he has an infinite motor. He lives for the big moments and seems to always lift his game in the clutch. He loves doing all the dirty work (fighting for loose balls, rebounds, etc) that most guys are afraid to do. He wins is a ton of extra possessions at key moments in games because of his hustle and physicality. He's improved this year as both a passer and a ball handler, and is doing a much better job at getting to the line as well. He takes pretty good care of the ball and has had a very solid assist:turnover ratio ever since he came into the league. He ranks among league leaders in charges taken - a huge stat since a charge not only gives your team possession, it also counts a foul against the opposing team.
On the other side of things Smart is extremely undisciplined. His shot selection is terrible more often then not. He's hot tempered and struggles to keep himself composed in the heat of the moment, which often hurts the team. He has a tendancy to commit ill advised fouls at the very moment when the last thing you want is an ill advised foul. He tends to throw up contested threes early in the shot clock when all you want/need is a high percentage two. He's extremely inconsistent on the offensive end - probably the most inconsistent player on the team. He flops way too much (often they are laughably badly acted) to the point where he is starting to lose all respect from officials. He complains so much that he's among league leaders in technical fouls (which offsets the charges taken - because it adds a foul against your team AND gives the other team possession and a foul shot). He is a horrendously poor shooting 90% of the time, can't finish around the basket unless he is wide open, and has no midrange game to speak of.
Personally, I feel that right now Marcus Smart's strength outweigh his weaknesses - however he's walking a fine line, and there are moments where he crosses over to the point where I feel the opposite is true.
He needs to start by becoming more disciplined he needs to improve his emotional intelligence and his decision making. Specifically, he needs to be smarter at deciding when to shoot, when to flop, and when to argue/complain. Those things are all mental, so if he really puts his mind to it he should be able to slowly make that change. IF he can do that, it'll go a LONG way to convincing me that he has a long future on this team.
If he can develop his offensive ability, then that's just a bonus.
If he continues with the poor discipline, I'll be concerned about him becoming a less talented and shorter version of Rasheed Wallace.