I'm actually a bit worried about Topp winning. I think he has the capacity to be vindictive and he has certainly thrown elbows in this race. Topp also knows that once you've won, you've won, and I don't think he'd be shy flexing his power. Mulcair on the other hand has taken a lot of hits during the campaign from inside the party, from all directions. It seems to me that he would have the biggest team-building exercise on his hands and is probably aware of it. Evenso, he has been endorsed by more than 40 NDP MPs, including a former rival. Not bad for team-building. How he has campaigned seems to me indicative of how he would behave as leader. He hasn't tried to "crush" his opponents or intimidate candidates out of the race. He hasn't campaigned negatively with the exception of 1 comment about Topp not having lived in Québec in decades at the very beginning of the race. Nash has run a very positive campaign as well. With the exception of a few attacks on Dewar and Topp in the debates, she has publicly taken the high road. Nash also comes across as a genuine, nice person. I'm not worried about her ability to "play well with others."
I actually believe that the left flank of the NDP might be better off if Mulcair wins over Topp. At least in Mulcair's case, the left flank knows that Mulcair is not on "their team," so they can strategize around that, and Mulcair would have to reach out to them in order to do well. Topp, on the other hand, is clearly saying things he knows the left flank of the party wants to hear, but IMO he knows who he has to cater to, and the left could end up marginalized because they think he's "one of them." Topp was in high places under Romanow's government in Saskatchewan, and Romanow was no lefty.