With all these features and content is the game worth getting. The short answer is yes with a but. At the end of the day, Brawl is still a fighter. It's a really good fighter, and probably one of the best ever produced in the genre. It's absolutely feature packed and really balanced. But if fighters don't do it for you chances Brawl won't either. With fighter fans in mind however, this is probably one of the best packages to ever come out in the genre.
You've got good offline and online play, enough customization that you can tweak it to your play style, insane amounts of unlockable content, mini game events, and a nicely presented adventure mode. Brawl is real value as for as content goes and it's something that will probably get scratched to death before you truly shelve it.