The most irritating thing about the h264 rant is that there are some valid points in there: content producers would have to encode content twice, lack of hardware decoding, pushing video back to Flash, proprietary nature of VP8's development. But these all seem like short-term problems to me. Hardware decoding will happen and Flash will support WebM.
The biggest long-term sticking issue to me is Apple. They have a lot of weight to throw around with iPhones and iPads, and it seems h264 is unavoidable there. Google could throw its own weight around by switching all of YouTube to WebM, but that would take some time as hardware and software catch up. In the meanwhile, Apple is selling millions upon millions of h264-only iOS devices.
And there's the patent issue too. It'd be nice of Google indemnified WebM, but they also have enough patents that they could cause problems for MPEG-LA too.
The last one I remember was when he spent weeks snarking about how Google was somehow being dishonest about not using private APIs in Android. The reality was Gruber hadn't spent 5 minutes looking at the intro to the Android SDK document, and fundamentally misunderstood how Android is architected. What really made it ridiculous is that he kept on with it after having been corrected on the matter, with one of those corrections coming from no less than Tim Bray.
Basically, Gruber is great when he sticks to Apple analysis; when he strays into discussing the competition he tends to enthusiastically dig himself a hole.
EDIT:
Here's that response from Tim Bray I was referring to:
http://www.tbray.org/ongoing/When/201x/2010/05/06/Private-AP...
Gruber was conflating internal datastores with private APIs. The official Android SMS app uses public APIs and then stores messages in its own internal datastore. Bray was cautioning app developers that they shouldn't access that store because the SMS app is not part of the core framework, can be replaced by other applications, and is not guaranteed to be there on all devices as a result.
Gruber managed to turn that into constant snarking about Google lying about only using public APIs.