I have to agree w/ svt about the musicians part. That was the second time a scene like that came up in the book, and I could see why Kerouac would want that in there but it was pretty boring.
When Sal meets Henry and says that he reminds him of young Dean, and proceeds to give him advice, Sal seemed like a father figure to this kid. But the difference between Henry and Dean is that Dean never had a father figure to advise him like that, and maybe that's why he's so impulsive and crazy. And speaking of impulse...at the beginning, Dean seemed to just be stealing car after car within a short amount of time, which was a little strange to me.
There was a quote on page 253 that I liked, where Sal is talking about how his kids would see the pictures Ed Dunkel took one day and think that he and Dean had lived "smooth, well-ordered, stabilized-within-the-photo lives." Which shows that even though something appears to be one way, it might not be. This is also true of the lifestyle they lead; one would think that traveling all over and doing everything spontaneously would be a lot of fun, but they're not really happy.