The ultra thin laptops would certainly work. The doctors I’ve worked with like the simplicity of the tablet. They don’t have to worry about opening or booting as they walk around.
Yep. Perhaps you should read this article. I think the iPad will be very hard to displace in the medical field, and your HIPAA concerns are easily addressable. Doctors will want the same great experience as they've had with their personal iPads, and Win8 is unlikely to deliver.