About 50% of a typical MD/PhD interview is devoted to finding out if you're committed to an MD-PhD. If you're waffling, I suggest you not apply, one of the reasons being that your indecision will likely shine through in your interview and you will be passed over (and in my opinion, rightly so) for candidates who are more likely to stick through the program. Then again, you might be a good actor, and it might not matter, but ADCOMs have a lot of experience figuring these things out.
If you are an MSTP (the NIH's "official" MD-PhD program), you are not liable for MD-PhD tuition should you quit, although it still is a bit of a gray area and schools have threatened quitters in the past. If your school has a separate funding source, policies vary. Unfortunately, it's not a question I'd ask at an interview.
Whatever the case, you will not make friends unless you have a very good reason for dropping the MD-PhD. It is considered something to do for only serious and undpredictable reasons, like illness in your family or your PI moving to China. The MD-PhD people at your school probably won't make your life miserable, and you will match somewhere, but pissing off a number of faculty becuase you lied to them (told them you were passionate about MD-PhD at the interview, then quit for trivial reasons) is not a good way to start a medical career.
Thus, I suggest you take more time to think about what it is you want from your career before you apply, or apply as an MD-only and then to an MD-PhD program at that school after your first or second year, which can be difficult at some institutions (ask about it at interviews, it's definitely an acceptable question to ask at an MD interview, as in "I'm not ready to commit to MD-PhD, but I'm interested, what's your policy on that, how many internal applicants do you accept per year?")