Cleveland Clinic is as non-malignant as they get. Dr. Nielsen is the nicest PD in America. Remember that Simpson's episode where they move to another city and homer gets a new job at a new reactor, and his new boss is an energetic, super-friendly guy who has plans to take over the world (they kill James Bond in that episode). Yeah, well Dr. Nielsen is THAT nice (minus the world domination plans). Honest.
I graduated from the Clinic 2 years ago and think it is an excellent program. I've spent some time in UH and felt that the environment there is more aloof and elitist (and the Hospital smells and cafeteria sucks). The fellowship match results are to my knowledge fairly comparable. Clinic I believe has some of the sickest, most complicated, highest acuity patients in the nation (and I'm currently at MGH) and will provide excellent training for general or subspecialty practice.