When I was suffering from depression, marijuana amplified my emotions like crazy. I didn't really find this to be a bad thing though; I have a bad habit of ignoring my feelings and circling around them like they aren't even there, but when I was depressed and smoking a lot of pot, I felt my feelings to their full extent and actually worked through them instead of ignoring them.
Ecstasy seems to be the only chem that really amplifies my emotions in a way I feel in touch with them, marijuana was fun for a few years but I tended to get pretty extreme paranoia and confusion the last couple years with it. I could probably still smoke a joint on occassion if I wished but hitting bongs fucks me up real good, shits too intense.
That's how it is for me too. Not only does weed make me happy while I'm stoned, but it also helps me concentrate on my problems and work through them in a positive way, instead of just drowning in self-pity. It adds perspective and also the knowledge that everything will be alright. Many people say it's just a way of running from your problems, but it's quite the opposite.
I personally think everyone needs to smoke ganja...the world would be a better place. Everyone would be just too stoned to steal, rape, or kill anyone. Theft of grocery stores would definitely go up though.