I have read stories from being on this board for a few years of students without MS3 required neurology rotations having trouble arranging a 4th year schedule as they have to make sure their neurology rotation is in the first few months to get letters and check out the specialty etc. For me I already had done a rotation by the time 4th year started, then I could do a 1 month pseudo-sub-i at the beginning of 4th year and have some great letters by the time my apps were going out
I have also heard of some schools that don't have a neurology residency program associated not even having electives to take and then they all have to be arranged as aways, which I always thought seemed like a big PitA once you figure in getting alternate housing etc