im gonna add my 2 cents to this long argument
up until march, starting in about october, i used to smoke at least once a weekend. i stopped doing it because i realized i didnt need to. i mean of course i liked the feeling of getting high, but i saw myself as throwing away my money for something that i didnt need. plus, i needed more money to spend on my car. i am around potheads all the time, and from what i have seen, it does slower reaction time. but while driving, it makes people more cautious, and is nothing compared to a drunk driver. the only real negative effect that i have seen, is that some people who have done weed, have moved on to harder drugs, such as heroin and cocaine. i myself would never go near any other drug besides weed. but thats all i can tell is truly negative from my experience. it didnt ruin my goals at all or anything, and hasnt affected me or changed me.