Pros: 98% of the time it helps with my mental illness. I used to have bad insomia as a child, and it helps with that. I used to get night terrors up until I was 14 then I smoked cannabis for the first time, and it was like it was gone overnight. One night I'm screaming in my sleep, the next, I'm not making a sound. I don't even snore. :p
Those are my pros, but when it comes to helping the sick and suffering with deadly illnesses, I think that is def. a pro. Pills can have nasty side effects, I know that, but what I take is nothing compared to what people with crippling illnesses have to take, like 12-20 pills a day. I think it's great that we can reduce the number of pills by only taking 2 or 3, or even 0 pills, and replace it with a naturally growing plant, with no serious side effects. Medicinal use is a great pro over those nasty chemical drugs.
Cons: It can make me sleepy sometimes if I over-smoke. What I mean by that is continuing to smoke when I'm already high, which is pointless. It costs money, a lot of money, but I'm willing to set aside $200 every few months for a nice sack of smoke.
It slows my mind down big time, so if I'm doing something that requires a lot of brain power, or if I'm learning a new job at work, then smoking is out of the question. I don't retain anything thsat I have to learn while high. It makes learning fun, but there is fun learning and serious learning.
EDIT:
www.cannabisculture.com has lots of amazing medical info and growing info. It's a magazine based out of Canada.
There is also another one out there called Cannabis Health magazine, also Canadian and is free at the headshop here. It focuses directly on medical uses of cannabis.