Right now, I'm trying to get a blood test for Vitamin D, but all the doctors I've gone to see are ignorant of the latest Vitamin D research, and don't see the value of doing the test. If I can't find a doctor who will authorize it in the next year or so, then I'm probably going to drive down to the US and pay cash using Direct Labs (http://www.directlabs.com/) or the Life Extension Foundation (http://www.lef.org/). It's terribly inefficient but I don't see any way around it.
Vitamin D and Calcium Supplementation Reduces Cancer Risk: Results of a Randomized Trial (http://www.ajcn.org/cgi/content/abstract/85/6/1586)
There is also a lot of information about vitamin D research at the Vitamin D Council website (http://www.vitamindcouncil.org/).
That being said, I don't know if taking a vitamin D supplement would have any noticeable effect on your sense of well-being. I think it's probably a good idea to take one even if you don't notice a difference.
Because of the compensation model, they've embraced conveniences like e-mail, phone calls and text messaging for communication, as well as once-common house calls.
They're also able to better-compensate their doctors and provide longer, more immediate appointments because they don't have nearly the overhead of an insurance-financed medical practice. This could help stem the tide of doctors leaving primary care practice (http://www.entrepreneurialmd.com/index/2008/11/18/angry-prim...), a trend which does not bode well for the future state of preventative medical care.
It's a very early trend, but I'm looking forward to seeing it develop. I currently know of Qliance (http://qliance.com/) in Seattle and Hello Health (http://hellohealth.com/) in Brooklyn. For more, you can check out videos from each organizations' founder: Dr. Garrison Bliss (http://www.tvw.org/media/mediaplayer.cfm?evid=2008030136C...) and Dr. Jay Parkinson (http://vimeo.com/2082073)