Example (most recent):
http://daringfireball.net/2009/01/macworld_expo_predictions
He was just about as wrong as one could be on anything that wasn't expected or scheduled to be announced.
As for Twitter, based on the times he posts and the amount he posts:
44 posts (result of search for "twitter" in his own site search box)
That's a lot ... seeing as he's under 1500 total posts for the whole site.
Twitter is a huge buzzword right now ... it's being pitched by the geek elite like it's some kind of miracle form of communication ... Gruber fits into the category of "Geek Elite" that likes to pretend he's hip with everything.
Don't get me wrong ... I don't hate him and I don't mean to bash him here. I just think he's a huge prick who's had some big success being a wannabe by association. Sites, such as this one only link to him for the same reason they use DIGG or Slashdot to promote their stories - hits!
To be fair yet agree with your comment:
I think everyone doubted an Intel switch was coming ... I know I did.
But, if he were as connected as he claims to have been, he would have gotten that right, because that has been almost as big as the iPhone in terms of Apple announcements over the last decade.