Depends on the school, but other than HBS (where the interview is make-or-break), all interviews are just another datapoint in the application. Everyone who gets in has to do an interview, but not everyone who does a great interview gets in (i.e. interviews will more likely hurt you than help you - a great interview won't automatically translate into an admission, but a bad interview can certainly turn the tables against you).
So the answer is no - you're not home free just yet.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com