When I did a rotation at another university's hospital, i saw a nurse wearing a big button on her coat, saying: "Oncology nursing is NOT depressing!"
I guess it depends on whether or not you can handle treating some folks with terminal illnesses. Some people can't or won't for whatever reason.
As far as I know, chemotherapy and some hormone therapy is all medical oncologists used to fight cancer (and their pharmacologic armamentarium for side-effects). Radiation is left to the radiation oncologists and surgery is left to the surgeons (gyn onc, urology, surgical onc, gen surgery, colorectal, ENT, etc.). I guess some academic oncologists are now dabbling in bone marrow/stem cell transplantation as well.
I have not done a formal hem/onc rotation, but the clinic side is very busy as I spent 1 onc clinic per week during my month of ambulatory IM. I can't say much about inpatient.
-S.