There are no more slam-dunk approaches to practice at this point. The sky is not falling, but the field used to be a license to print money, but it's just not that way anymore for many reasons.
There are good and bad practices everywhere and can be configured in a number of different ways (private group not employed by hospital but charges only professional fees with service agreement with hospital, private group that owns machines, private group of doctors that owns their own cancer center, employed rad onc by hospital et al). Speaking generally, the risks of a true PP group include not ever really making partner, while the risk of hospital employed is more the "cog" phenomenon or some administrator deciding you make too much (trust me, MGMA helps, but they can hire their own "consultant" to determine whatever market rate they want it to be) and cutting your pay or finding someone else. The over-supply issue comes into play here, because your value/negotiation power in both of these situations is hampered by a potential glut of cogs/junior partners.
Like Nueronix says - you've got to be your own advocate and look out for what is in your best interest. Call former employees, talk to the referring docs, and talk the competition in town. Talk to former residents or anyone at all about how practices work and what the place is telling you and if that jives with his/her experiences out in practice at all. If it sounds too good to be true it probably is.