I don't think smoking weed necessarily leads to other drugs, but I have to say that my attitude towards other drugs has changed a great deal since I started smoking pot. I think that now I do consider trying stuff that I wouldn't have even thought about before smoking pot. Funnily though, I have no curiosities about the drugs that are commonly the ones that people are afraid weed leads to, namely heroin, E, coke, crack, etc. and have become more interested in spiritual substances like salvia, shrooms, and DMT which I would only take on very rare occasions, i think weed is still the only drug I'm comfortable using habitually, so I guess in the important ways (i.e. chronic use of very harmful substances), weed's not a gateway but like Ghost said, you're the gateway. I'm happy where I am.

BB- first off, i don't start developing serious immunity/tolerance unless i've been smoking all day every day for a while, but when I do, even a few days off will get me back to light-weight status . If you smoke in moderation most of the time, it probably won't become a problem just because of the time, I think quantity is a big factor in figuring how high the tolerance goes. Sometimes i'll smoke a J, be high for like 20 minutes, and then feel nothing, and that's when I know I've been smokin too much.
Also what helps sometimes, is going out drinking and getting disgustingly wasted. I find that when i'm hungover, a doobie is the greatest medicine, and I realize the beauty of the buzz in contrast with the confused pointless alcoholic stupor I was in the night before...

peace

ps- cool poem BB.