I concur, having recently been through the fellowship interview process for Endocrine (to start july 2004): It's not competitive. Maybe because it's not a sexy, high octane specialty like Cardiology or Critical Care? I decided to do it bc (1) I want to subspecialize but still be able to practice general medicine, (2) I like diseases that affect the whole body, and (3) it seems endocrinopathies are often the answer to the really interesting cases with mysterious presentations (perhaps second only to Rheum). (4) I also wanted to have regular hours to facilitate having a family.
I considered Rheum, and was quite devoted to it for a while, until I realized (a) I hate fibromyalgia, and (b) Rheum diseases are so vague! With endocrine you have symptoms, you have a series of tests to rule diseases in or out, and then you have treatments that are straightforward, and you have numbers that you can watch to monitor response. What could be more satisfying? Contrast that with Rheum where the disease is some nebulous overlap of two oddball diseases, the treatment is toxic, and the monitoring consists of tracking symptoms that are often so vague.