The new special features for this anniversary edition include a four-part retrospective with those who worked on the movie returning to talk about how it all came together (a lot of this hinges on Affleck and Damon and, oddly, their friend and fellow filmmaker Kevin Smith). Minnie Driver doesn't appear, and it would have been nice to hear from her as well. Even so, it is an incredibly interesting piece and well worth one's time. It is proof that these sorts of first-hand recollections of films from our recent past can be produced in relatively simple fashion (this really is just a bunch of talking heads) but can still be incredibly interesting. Another new feature has more talk from Damon about the movie and is somewhat less good but still worth the effort. Older special features reappearing here include a commentary track, deleted scenes, an EPK-style featurette, the Academy Award montage (which really ought to have been redone 16:9, not a letterboxed 4:3), behind the scenes footage, and a music video for the Oscar-nominated song.
As for why I wouldn't buy this version, that's because for a couple of dollars more (at Amazon it's more anyway), one can get last year's release. That doesn't include the new featurettes, but it does include a digital copy of the movie. Readers will have to decide for themselves whether they'd rather have the new retrospective or the digital copy, and I have trouble understanding why that choice is required – clearly the digital copy exists, it doesn't feel like it ought to have been too difficult to include it here.
As for the film itself, 15 years later Good Will Hunting is just as impressive a movie as it was upon its initial release. Damon and Affleck's careers have diverged and varied, but to many the two men will always be inextricably linked due to their work here. It is a film worth owning and worth watching again.