True. I don't know if Paul writes his own music or lyrics, but even he wouldn't get far without a backing band (whether it be musicians or backup singers, or both).
True. I remember GnR as they were in the early-to-mid-90s, though; I haven't followed any of their music since, although I'm aware they'd gone through a whole bunch of other musicians.
Very true. Music is a collaborative pastime (and business). Some egoism is healthy; it's important to be confident in what you do. (If you're not, why should anyone listen to you?) It's only when it goes further, and becomes arrogance - that won't win you any friends. (Then again, that's true in most other things, too).
I suppose fame goes to people's heads. If you're level-headed enough to deal with it, it doesn't become a problem -- e.g. I always respected Slash for not letting fame go to his head. He just keeps his head down and gets on with it.
Bono came across as being a bit of an egoist in the past, but it's a credit to him and to U2 that they stayed together for as long as they have.