We're a little ambivalent about robots performing surgery autonomously and unattended, but there are clearly cases where it'd be beneficial, and it seems like an inevitable future. Duke researchers working on robo-doc lab feasibility studies announced this week a proof of concept using 3D ultrasound mapping to enable machines to "see" what they're doing. The first test procedures have focused on use of those ultrasound transducers in catheter-based procedures using fluoroscopy, so it sounds like we'll still have a few years before we say ahhh for a machine.
http://www.engadget.com/2008/05/08/duke-inches-toward-autonomous-robo-surgeons/