Just because your doctor is using a computer doesn't make your information secure. I've been to plenty of offices and hospitals that have their computers sitting out - with the power button available and USB ports open. If you can reboot a computer - you can get in.
True but, in part, that's negligence on the part of the IT department and/or the doctor. Beyond that, losing a tablet is a much more likely scenario than a workstation (not to mention theft). So, I agree that being on a computer doesn't make it secure beyond doubt but I do think it is a much more secure option than a tablet (of any variety).
You can have data encryption - wireless encryption - vpn - remote wipe etc that can secure data. If the DOD says they can use an iPhone/iPad/Android - it should be good enough for medical use.
I don't have an issue with tablets in medicine in theory but I fear that their design as consumer devices makes them problematic for a field that uses devices in very different ways. Now, if data was streamed (over secure connections of course) and not stored on the device, I might be okay with it.
And here I sit in a city that,
more than a year ago, rolled out more than 3,000 iPads to doctors and hired 70 developers to create applications specific to the needs of doctors and nurses. Looks like I might be on the wrong side of this debate (despite my reservations).