MJ: I'm not so sure I would retake the MCAT if I were you. Here's why... First, it seems as if your score and your GPA were competitive enough to get you interviews in the first place. I'm sure people have varied opinions on this, but it is my understanding that an interview means you have passed their initial screening criteria. So your 28 MCAT did what it needed to do. So, if for some reason you don't get in this cycle (don't lose hope!), I think you should contact the a&M, tech, and houston Adcoms and see if they'll recommend any areas of improvement. It might be clinical volunteer hours, ECs, interview changes, etc...
Secondly, I don't think you should retake it because it IS such a hassle (and an investment) to study for the darn thing all over again. There have been people (including myself) that have already gotten pre-matches this cycle with lower GPA's and even lower MCAT scores than you. Unless you are shooting for the stars (UTSW, Baylor, etc), I'd say you should keep your 28.
There's my $.02, for what it's worth!