Re Flash GL accel - last I checked this had to be forced on for everyone running FOSS drivers. Not to mention GL accel is on older cards worse than x11, not to even mention xv.
Hi guys, the follow-up post mentioned in that blog entry is now available, and explains the thought process better, and answers the questions posed in the previous blog's comments, plus some other common questions about Flash, CPU's, and GPU's.
I don't necessarily see anything wrong with companies choosing to implement vdpau acceleration in their drivers, it's certainly possible. But the real question is why should they? VAAPI already supports Intel + ATI (sort of) + Nvidia, so it doesn't make much sense from their perspective to suddenly change their development to focus on a different API that nvidia is pushing for.
I mean, sure it's a little buggier for now, but if they all suddenly switched to vdpau their vdpau implementations would all be even buggier. Hopefully they'll get all the bugs ironed out soon.
You might want to check out http://video.linuxfoundation.org/video/1575 as it also covers some yet untapped potential of vdpau.