Marijuana has never made me lazy...As a matter of fact, it makes me want to clean my house from top to bottom! I have a girlfriend who experiences the same thing. I've also been known to want to create things (reupholster furniture, sew, paint, etc) when I smoke pot. My sex drive does not decrease, and I enjoy having sex after smoking pot. (My hubby says that it makes me less inhibited.)
I think that if your predisposition is laziness, then yes, pot would make you more lazy. But with creative, artistic types like me, it just emphasizes my ambition and creativity.
I also believe that pot has made me want to learn more, and question everything. It is my FIRM belief that pot makes you less likely to be indoctrinated.