As silly as the people screaming that Nintendo are destroying the industry or abandoning their fans sound, there was barely anything in the conference aimed for people who've been playing for more than a few years. GTA DS was the only major new announcement, and even that's very likely to be crap.
Then again, they announced Brawl as a suprised after all their other conferences a few years ago. There's still probably going to be something interesting announced... sooner or later.
I really want my 30 minutes back, though.
To a certain extent, I think Nintendo believes that their "Media Breifing" is a good opportunity to target people who aren't "Core" gamers because it is (potentially) the only part of E3 which gets a lot of mainstream media outlets attention ... Showing off a game (like Brawl) at a different event or behind closed doors will still get a ton of attention from the dedicated gaming press which will get the attention of "Core" gamers.