I think the future of heme/onc is bright. A couple years ago they were saying cancer is suppose to overtake heart disease as the #1 killer in 2010, so oncologists should be in high demand. Plus, people are living longer and the incidence of cancer rises with age.
In terms of reimbursement, I'm not sure with all the health reform stuff. As of Jan 1st, cardiologists will be reimbursed 40% less for nuclear scans and something similar for echos, which will have a domino effect since those are the usual indications to take a pt to cath besides STEMI. I don't think there's been an equivalent cut for heme/onc, but I doubt it's far off. However, Obama did allocate 5 billion of the stimulus plan for cancer/AIDS research.
Irregardless of reimbursement, you should choose the field you like because in the end you'll be working 8hrs a day doing that job. A lot of people went into anesthesia for money, but now they are planning to give one time "bundle reimbursements" to hospitals for surgeries. GI was not popular until the 90s when guidelines for screening colonoscopies came out, but now CT colonographys are coming.
The best way to see if you like heme/onc is to do an in-patient rotation and an outpatient clinic. Harrison's is great for bread and butter and has way more than you need to know as a med student, plus you can use it for other stuff besides cancer.
