Assuming you can even manage to get accepted to such a program in the first place, I would only do it if you know you'll be happy at that med school. That means that you like the school, are okay with the tuition cost, and won't regret passing up better schools should you find yourself in the position where you know you have an application that would be competitive for schools you previously thought were a dream.
If all that's okay, then I say do it. I'd say ignore people who say you'll be wasting your undergrad years. A BS/MD gives you guaranteed admission as long as you meet a very low bar throughout college. This means that, if you so wish, you could ignore all the stuff normal pre-meds have to do: Volunteering, research, shadowing, cramming for the MCAT, and obsessing over every point in every class. At the very least that will cancel out the time commitment issue. Obviously you shouldn't ignore ECs like that, but the point is that your time is MUCH more flexible. You'll have a lot less stress. If you need to take the MCAT for the program, they'll likely require a very low score that virtually anyone seriously considering med school should be able to achieve. Being able to essentially handwave MCAT prep is going to do wonders for your stress level and finances (especially since you'd be taking the test when the new version is still brand new). You'll need to keep a minimum GPA most likely, but it'll be lower than what you would need to successfully apply the traditional way. You won't have to worry about applications and all the stress and financial exsanguination that entails (getting LORs, writing essays, choosing schools, filling out secondaries, interviewing, etc).
All of that is well worth having to miss out on a few parties imo.
