I interviewed at UMC a few weeks ago. Here is my impression.
Most all specialties are covered, although they lack depth in some specialty areas. Location may be a problem for some people. Jackson is a smaller city (about 150k) in the deep south about 3-4 hours from Memphis and New Orleans. Resident interaction seemed very good and the faculty seemed nice as well. Call is apparently Q4 on wards in PGY1 and PGY2, but seems to lighten during year 3-4. Pay is less than other places that I have applied, but cost of living in MS is cheap. UMC seems very solid if you have an interest in living in MS.