Dan! This any help (gods this is long)?
Having looked up "Cannabinoids" in PubMed (The National Library of Medicine) I've found a few interesting things - sorry they're so sciency: (annoyingly so far I've only been able to access the abstracts (brief but complete summaries of the entire paper) so maybe I better go and get a new password so I can access the better online journals (hey, I got it over 2 years ago and haven't used it since, I can't even remember my damn username at the moment).)
Medicinal use of cannabis: History and current status.
CONCLUSIONS: Pure tetrahydrocannabinol and several analogues have shown significant therapeutic benefits in the relief of nausea and vomiting, and stimulation of appetite in patients with wasting syndrome. Recent evidence clearly demonstrates analgesic and antispasticity effects that will probably prove to be clinically useful. Reduction of intraocular pressure in glaucoma and bronchodilation in asthma are not sufficiently strong, long lasting or reliable to provide a valid basis for therapeutic use. The anticonvulsant effect of cannabidiol is sufficiently promising to warrant further properly designed clinical trials. There is still a major lack of long term pharmacokinetic data and information on drug interactions. For all the present and probable future uses, pure cannabinoids, administered orally, rectally or parenterally, have been shown to be effective, and they are free of the risks of chronic inflammatory disease of the airways and upper repiratory cancer that are associated with the smoking of crude cannabis. Smoking might be justified on compassionate grounds in terminally ill patients who are already accustomed to using cannabis in this manner. Future research will probably yield new synthetic analogues with better separation of therapeutic effects from undesired psychoactivity and other side effects, and with solubility properties that may permit topical administration in the eye, or aerosol inhalation for rapid systemic effect without the risks associated with smoke inhalation."
(Pain Res Manag 2001 Summer;6(2):80-91)
("Parenteral" means via a blood vessel, ie IV. And smoking pretty much ANYTHING will give off benzapyrenes, the major cause of lung/upper respiratory tract cancers - they're very flat molecules and can slot between the rungs of DNA, which stops it being replicated properly.)
I got 5479 results (or 274 pages) for "cannabinoids" (the active ingredient when you smoke it) so I'm not going to read all of them... (admittedly not all are papers, but there's a shedload of them there). Go to the website if you're interested, there's a lot of papers there on studies that have been done on it:
PubMed
Some papers are rather brain-melting (like "Desensitization of Cannabinoid-Mediated Presynaptic Inhibition of Neurotransmission Between Rat Hippocampal Neurons in Culture") but there's a lot of them there: "Involvement of CB1 cannabinoid receptors in emotional behaviour," "Cannabinoids: a real prospect for pain relief" and "Cannabinoids in pain management. Cannabinoid receptor agonists will soon find their place in modern medicine"
As a brief, general rule for how good a particular study is, look at where the paper was published. The big, important journals (like "Nature" and suchlike) get to pick which papers they publish, so they can pick the best (by "best" I don't mean the most user-friendly, I mean the most scientifically important, like groundbreaking research into new cancer treatments.). The smaller journals have fewer papers submitted to them, so they'll publish pretty much whatever they can. Smaller studies are less well financed, and so the results they get are not as good as the results from major studies.
Although as a pharmacy student (yes, that's right; drugs) I think I have a right to an opinion, I'm not going to say "yay cannabis is great" or "nay cannabis is evil" until I've read up some of these papers...
Actually, this looks pretty relevant to some of the things we've been studying, so thanks to whoever brought the subject up...