i tink sonic is one of the causes of delay...
Let's evaluate, ok?
July, - Sakurai announced Brawl would release on December 3rd, 2007
October, - Sakurai announced Brawl would release February 10th, 2008.
Do you really think that in 2 and a half months, they decided to squeeze in Sonic and delay the game, when since LAST SUMMER, Nintendo has been discussing with third parties the rights to characters? Sonic wasn't something just thought up in the past 2 months and then they said "oh well since we're putting him in let's delay the game" he must have been planned for at least the past 9 months.
The most logical reason for them delaying is that the closer it got to launch, the more they realized they want to increase the depth and content of the game, and that just won't happen by the end of November (when the game is supposed to go Gold and sent to manufacturing). I was watching the updates and stuff, and I seriously doubted how they could get the game as deep and jampacked as Melee was by the end of November. There weren't enough stages, items, game modes or characters announced in my opinion, and I felt they needed to work on it longer.
Since Nintendo is not like Sony or Microsoft where they can just release downloadable patches/updates/content, once a game releases, that's as good as it gets. So it's better to give them a little time to perfect and absolutely cram as much content as possible into the DVD than get something a month or so earlier that lacks a lot of stuff a little patience could have rewarded us with.
If you think about it, it's not that long. With Mario Galaxy and the bazillion other games out there for 2007, there should be other stuff occupying your time. Then you only got December, January, and about a week of February to play Brawl.
I am upset about the delay (mostly because they absolutely emphasized and promised it would be here before 2008) but if it's for the better of the game (like smoothing and fixing out online play) then I'm all for it a month or so of waiting.