Imho, GnR is the best rock band of all time, and believe the fact that they were so volatile was a primary reason.
Rock bands are at their best when they are angry. Once a band gets rich, their music is never as good. I saw an interview with Dee Snider (of Twisted Sister fame) talking about how their third album sucked so bad. He pointed out that what made their first two albums so popular was because of their rebellous messages. He said something to the effect of "It's really hard to be angry when you are sitting poolside next to your mansion, writing songs."
Even after GnR got popular, they never lost that edge... Well, until they imploded.
Yes, Axl is a primma donna. I remember waiting almost three hours in Tacoma for them to come on. He would never go on stage until he felt he was ready.