I'm not at Penn but I did get in off the waitlist and chose not to go - the biggest reason was financial aid (or lack of). Whereas Baylor (already inexpensive) gave me a full ride, the decision was basically set.
I could see Penn costing 40-50k a year...that can add up fast. I was in love with Penn after I interviewed there, especially the 1 and a half year of science. But Baylor offered the same. Anyway long story short if you get good financial aid I think you will love it there, most people said they do. Also the 1.5 yrs of science is like a Godsend especially now (end of MS1) when all I can think of is in 9 months I'll be in the clinics