I was on the fence about doing this program, because my stats are sooo boarderline for medical schools. This kind of made me scared to do the program. My reasoning has always been, if I can't hack it in this program, I can't hack it in medical school. Is the program comparable to the medical school courseload? Or is it harder? Is it one of those things where if you study hard you will be fine or are there some people that no matter how hard they try they don't do well? Also what if you need help with something? Are there resources/are the professors helpful or are you completely on your own?
What do you mean so borderline? If you spent a solid year taking classes (post bacc), studying/retaking the MCAT, doing research, and/or doing clinical work (depending on what your particular weaknesses are), would you be competitive and probably get into a med school somewhere? If so, my advice would be to do that, make your AMCAS as strong as possible and then simultaneously apply to med schools and BMS. IMO, an SMP like BMS should be a last resort to get into a US MD school. Kind of like
@lesterbarley said, you want to strengthen your application as much as possible prior to BMS since you will have very little time to dedicate to strengthening your AMCAS (the highest yield thing to do during BMS is study and max out your grades anyway). And if you ended up getting into med school directly, you'd have saved yourself ~$60K plus interest by taking that year instead of BMS right away.
I had the same reasoning as you, I figured if I couldn't do well in med school classes at a lower intensity course load than a regular medical student, then I wasn't really cut out for medical school anyway. Admittedly, the bare minimum threshold for performance is higher for a BMS student to get into CMS than for an M1 in CMS (i.e. you can't just pass your classes and continue on, like an M1 could, generally you need to excel).
In terms of difficulty, the classes are the same as the medical school (same exams, etc...), except you generally have way more time to study and dedicate to each class than a traditional M1. In that sense, it's easier to get higher grades since you can spend more time learning the details that will show up on questions and are necessary to get high grades. But again, it can be "harder" because you can't get C's and really low B's if you expect to get into CMS. Sure, some people got in with C's or lower B's, but I'm sure that not all of their grades were in that range. And those people very well may have had something unique or outstanding on their AMCAS application that is harder to quantify and generalize from. Personally, I went in assuming that I needed to maintain at least 85%+, and ideally all A's, to get into CMS. Going in with lower expectations will not do you any favors, even if people do get in with lower grades.
On the bright side, class performance seemed to correlate strongly with the amount of time I invested studying. Exams where I was really focused and putting in solid, efficient study hours every day, I did very well. Ones where I was burnt out or slacked off and admittedly didn't do as much work as I wanted or should have, did not go as well. I had the luxury of already holding a conditional acceptance by the time I slacked off a little, so there was much less pressure (I wasn't slacking off enough to worry about getting a C, so I wasn't worried about losing my conditional acceptance). In that respect, my advice would be to absolutely overstudy and kill as many exams in the first two quarters as possible. It may get you in early (which is an enormous stress relief) or at a minimum it will afford you a buffer should anything go wrong later. And something may, since spring quarter is definitely the hardest/most work by far (IMO).
In terms of resources for help, there seem to be plenty. Outside of reviews for exams led by older students or the occasional faculty member, I only really sought help from other BMS that I studied with or the occasional M1A TA. It really is a collaborative, helpful environment and people help each other out all the time. Someone mentioned something about the program being competitive earlier, which I completely disagree with. My friends would always help me when I needed it and vice versa. IMO, one of the best ways to learn is by teaching someone else and by being asked questions you had not thought of, so it really is in your best interest to help others as well.
I rambled a little bit more than I expected, but hopefully some of this is helpful for prospective/incoming BMSers.