I'm a Rheum fellow so my input is biased, but... You see the most downright interesting pathology as a Rheumatologist (at a large academic center) and you work with the most interesting system in the body (the immune system). We're not focused on a particular anatomic organ (heart, lung, gut, etc) which allows us to see the interesting cases that nephrologists see, as well as the cardiologists, neurologists, and pulmonologists. Look at the NEJM case reports--like half of them are rheumatologic illnesses. We actually have treatments that work now, RA patients today don't look like RA patients of yesterday, the research pipelines for future therapeutics especially in immunology (and heme/onc) is especially deep. Steroid injection for a painful joint has to be one of the most rewarding procedures out there. I've very commonly seen patients wheelchair bound in 10/10 pain walk out of my clinic. As mentioned in another thread, it is a great field if you want to do more research (particularly immuno) or if want to go into drug development/pharm.
And... last but not least, I cruise in to the hospital at around 8 or 9 each day while the poor 1st year nephro fellow has been in the hospital since 6 rounding on his ICU follow ups.
But you gotta do what you love...
