Pros: So called prestige..although only laypeople will know about Harvard. Apparently good specialization rate (most agree though that this high specialization rate is due to the students NOT the institution), some like Columbia and Harvard are PASS/NO PASS. which can take a great deal of burden off of studying. Good Research opportunities available which can help with chance of residency. many offer integration with MBA/MPH degrees.
Cons: Expensive. Very Expensive (like 340K expensive). poor clinical teaching (what if you decide to GP). Upenn is graded on A,B,C,D making it very cutthroat.
My take: Apply, it doesn't hurt. I wouldn't even consider Columbia and Upenn as they are expensive and not that great. If you get into Harvard, just ask yourself whether you are willing to take on the load of extra debt. It might be worth it if you are set on doing OMFS or are interested in academia. You are pretty much going to get into OMFS residency if you get into Harvard. If you are interested in other specialties, they are not that competitive as OMFS.
I would say if Harvard is within 50K of your cheapest alternative, then go to Harvard. If you have a school more than 50K cheaper than Harvard, go to that school. Don't go to Harvard.