NYU's approach to the admissions process is amazingly flexible. They do a holistic review of each applicant, so a bad SAT may not be the death knell for your Tisch aspirations. However, Tisch has a number of factors that isn't even approached in General Studies admissions process-- duh! Again, from what I understand, the two admissions processes are separate. How they finally come together is something you'd have to ask an admissions director about. Perhaps you go through the first process, and then if you get this far your tisch portfolio is considered? Maybe they're done simultaneously, and they come to separate conclusions and see where to go with things if a conflict arises? Either way, a bad GPA may not shut you out-- and remember, a lot of the application is under your control. You are writing the essay, you are writing the resume, you are submitting the creative piece... when the requirements aren't set in stone, you have a lot of room to make up for the downfalls. This still doesn't mean it's a walk in the park or NYU's a shoe-in for most people-- an admissions rate like 27% still means your chances are hurt by not having good test scores.
Chapman's admissions process, to me, seemed a lot more in-depth. The regular application was surprisingly long, and they asked for more on the supplemental application than any other school. They also had an interview over the phone...
Chapman's process was wonky this time around. From what I understand, they had a major influx of applicants to Dodge, and figuring out the new standards was difficult. The assistant admissions director told me only 10% of those who applied to Chapman's film school were admitted this year. That's intimidatingly low. A strong portfolio and creative work becomes more important if that specific major is that desireable. It's well below Chapman's regular admissions rate, and that's a big sign that a weaker GPA and test scores will affect your chances less than a dismal portfolio. As a whole, their average GPA is about 3.6 and SAT is 1250-ish (on a 1600 scale). That's lower than NYU's.
The other schools I applied to were slightly different. There was no supplimental app for BU, and Emerson specializes in "Communications" so their idea of a good applicant is built differently than that of a traditional University.
Good luck with your college application adventure. Anyone looking at USC should take a glimpse at their sup. app, because it's a doozy. If you're serious about going there, get your recommendations and materials lined up as soon as you can. But, again, the most important thing to remember is that freaking out gets you nowhere. Be calm. Be confident. And I guess I should say "Say no to drugs", but they work for some people...