While I was against the trade and think this is an interesting exercise, I do agree that the trade will ultimately be judged based on the playoffs.
Honestly, I think that if we look back at the trade after the playoffs, we'll see a repeat of this thread (unless we win the championship, or at least make the Finals). If we lose in the second round or in the semis, I think people will simply fall back on the argument, "Well, we wouldn't have won with Perk anyway, and now at least we have Jeff Green and a #1". I do think that if we win, most of the "anti-trade" people will come around, because I think most objections are based upon the worry that we made our team weaker, rather than an emotional attachment.
However, I don't envision a scenario where the "pro-trade" people change their mind, because there would never be a way to "prove" a different outcome. I think that many will continue to insist that the only backup 3 we could have gotten would have been Pavlovic, and will argue that that wasn't good enough. Anyway, I hope that this particular prediction is all academic, because I think we're all hoping for a championship; I'll be more than happy to put up with any "I told you so"s that might be coming my way.
I also want to point out that I don't really look at this as a "hindsight" debate. Everything that is up for debate was laid out at the time of the trade. Many people noted: Green as being extremely gifted but not aggressive or particularly good on D, Nenad having a nice soft shot but a defensive and rebounding game to match, and Perk being much more likely to return to health than Shaq for the playoff run.
Honestly, I wasn't as worried about Shaq's health at the time as I am now. I actually believed Danny that Shaq would be able to come back fairly soon, so in my mind, the trade looks quite a bit worse today than it did at the time. (I guess today looks better than yesterday, though, with the news that Shaq's most recent set back may not be that bad.)