Keck/USC just changed to tract system for Year 3 starting this school year. The order of the clerkships are set in 7 tracts and choose by ranking our preferences from 1-7. In addition to the Year 3 core clerkships, we also have a 6 week "flexible block" built into the tract that we can use to schedule whatever we want. The flexible block comes near the end of the year for most tracts, except for one that offered it at the beginning of the year for those who wanted more time to study for Step 1.
The major pro to this system is that since everyone on a tract goes through the same order of clerkships, the skill levels and competency of the students are similar. For example, you don't get the situation where you could be doing you first inpatient rotation 3 months in the year and get put on the same team as a classmate who has already had 3 months of inpatient experience.
The major con is that you are isolated with the same 20-30 students throughout the whole year. You see the same people on a daily basis in core curriculum and never see any of your other classmates.
Overall, I think it works pretty well, but that might be because I got my first choice of tract and we have an excellent group of (mostly) laid-back people.
