I had a similar situation last year. 3 days before an out-of-state interview, I got into a school I knew I would attend over school X. My rationale was that I was wasting everyone's time (including my own--it was a 6-hour car trip away) by going to the interview, and that there would be another applicant who would be more than happy to take my place and could do so on short notice (this was a state school--not my state, though--with a largely local applicant pool). I checked with my pre-med advisor, who told me that I should cancel.
I would have been hesitant to cancel on a school with a national applicant pool, however, as finding a replacement interviewee on short notice is more complicated. I have heard of people getting yelled at by admissions officers (e.g., Stanford), but I never heard from the school (not even an acknowledgement of my cancellation/withdrawal).
I wouldn't apply to G-town for residency, though. 😉
Congrats on your acceptance.