If you've been listening to his podcasts or actually reading his blog, you would know that gruber has no better information (and, in fact, usually less advance knowledge) than the random rumors on macrumors/apple insider. He usually trails both loopinsight and allthingsd in terms of scoops and confirmations. He is anything but an "insider."
For the last several years about the only "inside information" he's received is a week's advance use of loaner laptops/iphones so that he can write a review column. (Same thing that Pogue, Mossberg, and other prominent columnists get, and he's subject to the same embargo as they are.)
All gruber really has beyond his extensive network of colleagues in the industry are his presentation skills, his writing skills, his love of Apple, and his appreciation of things well made.
And, to refer to Jean-Louis Gassée as "someone ..so blinded.." would suggest that you have little understanding of the history of the industry, and who Gassée is.
Take 5 minutes to read: http://en.wikipedia.org/wiki/Jean-Louis_Gass%C3%A9e - you'll come away more informed. He's one of the major figures in the history of computing.
Gruber is partisan, obviously, but it doesn't detract from the intellectual rigor of his repudiations. His latest one was spot on - the NYT columnist that Jean-Louis was referring to had stated that in the Jobs era, stock prices would routinely go up after a product announcement, and in the Cook era, things are not so bright. Gruber took the 20-30 minutes to go check that fact (something the NYT clearly didn't bother to do) - and discovered that, in fact, it was a mixed bag - and the stock dropped as often as it went up.
Not sure what "propaganda" you see in that.