I can't say he will do good or bad. We can only wait and see. My feeling is that he will change alot, from coach to management and that is a brave decision (not Allegri because the results speak for themself, but the management).
This mercato we have the chance to build a new Juventus, with a new coach and many new players. Some will say that we don't have alot of cash, that can be true even with CL and World cup coming up it's hard to know how much money we can spend.
But I believe many players will leave, many of them we will be happy about them going, one or more will hurt, but for me the most important thing is that we become a better team next season, and that's Giuntolis job.
A example was De Ligt leaving for 70-75 million euros, a great talent but in the end we got Bremer who IMO is better and cost us less then De Ligt, this deal was before Giuntoli, but just a example that you can make a sacrifice that hurts, but in the end you made a good deal from both a sporting and economical point of view. So let's see what Giuntolis does this summer. Will he keep Rabiot? Sell or keep Soule? Hujisen? Mckennie? Chiesa?
Give him a chance atleast.