The main features of the NextGen program is introduction of the various phases rather than clinical years (MS1, MS2, MS3, MS4) which practically turn the the curriculum in 14 months of pre-clinical and the rest clinical clerkships; in essence its a 1 + 3 set-up.
One of the education techniques they are using is symptom based curriculum which really helps put students in the thought process of determining clinical differentials. While a traditional organ system might seem to be easier in terms of studying as one can just focus on one organ and move on to the next, in practice biological systems are never isolated as a patient is going to come in and complain of symptom(s) and you go from there. For example: chest pain causes could be cardiac, respiratory, GI related etc. etc or a combination of all of those. A lot of physicians and midlevels that I've worked with have told me that they would have loved to have that type of curriculum as it is a direct parallel to the thought process they use in practice.
The 1+3 set-up allows you to start doing clinical clerkships a year earlier and start getting exposure to various specialties along with honing your skills. I think the early year of clerkships is also really beneficial as it can help you decide what you like or what you don't like as you start preparing an application for residency.
As we start clerkships earlier, there is a scholarly concentration component that allows you to pursue a dual degree in 4 years, have dedicated research time in years 3 and 4 that can be really beneficial for competitive specialties, or potentially graduate in 3 years (note that for this last point it was briefly mentioned in second/third look and they haven't specified the details of the 3 year MD.)
Grading wise, phase 1/MS1 is confirmed true pass fail, and the first part of phase 2/MS2 they are actually planning to make it true pass-fail clerkship grades as well but it hasn't been confirmed yet. Phase 3/ MS3 and MS4 will have grades.
The MD students rotate in Jackson for phase 2 and the MD/MPH cohort rotate in Palm Beach JFK and public health related clerkships. For example, for the psychiatry clerkship there is a public health focus in which you will also be in an outpatient community psych clinic for individuals living with HIV/AIDS, and for family med at a clinic with a focus on uninsured immigrants etc, etc. Phase 3 you decide where you want to rotate regardless of whether you are MD or MD/MPH.
Granted, this is the first year of the program so I'm sure they'll be some quirks along the way but it seems very promising and they have been experimenting with certain components of the phases with previous classes so it won't necessarily be a totally blind run.
Hope this helps!