This song is about how heroin affected the band. Mr. Brownstone is likely to be their dealer. Brownstone isn't a common slang term for heroin, but it is brown, which is likely to be where the dealer got his name from. (thanks, Sterv - Donny, England)
Axl Rose's lyrics mention how the band would take heroin before performing at concerts. "The show usually starts around 7, we go on stage around 9" means they were two hours late for the show because of the drug. Later he sings: "Now I get up around whenever, I used to get up on time," meaning he doesn't care anymore about it, he's so obsessed with heroin.
At the end of the song in the lyrics: "Shoved it in the bindle and I shot it in the middle And it, it drove outta my mind I should've known better, said I wish I never met her, said I leave it all behind," A bindle is a "dimebag" full of heroin, he shot it in the middle, getting rid of it, and says he wished he never met her (her being heroin) and he just quit it cold turkey. (thanks, Matt - Woodstock, Canada, for above 2)
Velvet Revolver, which was formed by three former Guns N' Roses members, regularly played this at their shows.
While opening for The Rolling Stones at a show in Los Angeles on October 18th, 1989, Axl Rose said on stage: "Unless certain people in this band get their s--t together, these will be the last Guns N' Roses shows you'll f--king ever see. Cause I'm tired of too many people in this organization dancing with Mr. G--damn Brownstone." It apparently got the attention of his bandmates, as Slash, Izzy Stradlin and Steve Adler promised to clean up.
Axl Rose, on his reputation for starting shows late: "I pretty much follow my own internal clock, and I perform better later at night. Nothing seems to work out for me until later at night. And it is our show. I don't want to make people sit around and wait - it drives me nuts. That hour-and-a-half or two-hour time period that I'm late going onstage is living hell, because I'm wishing there was any way on earth I could get out of where I am and knowing I'm not going to be able to make it." (thanks, Bertrand - Paris, France)