I could not get ATI hardware acceleration working with my 2400 Pro. Customer support was less than helpful, saying it was a driver issue and that I needed to contact ATI. 7.3 accelerates just fine on the same machine.

seems weve just got to percivere just now.
i got a reply from the techies and it turns out there is a few problems with this new version and there working on a patch to resolve the issue.
if you cant wait till then, anydvd which works along with your blu-ray/hd drive helps massiveley try the free trial for 21 days hopefully patch will be out by then

AnyDVD did not help the hardware acceleration issue in my case.

they may be right in it being your catalyst driver i have had some issues with these aswell although not with hardware acceleration. it seems strange that it worked with 7.3. have you tried updating the driver via device manager in windows instead of the catalyst installer, because i ended up using that many drivers all the way from 7.9-8.4 for one different problem or another i had to do a complete uninstall of them all and reinstall the latest version. As it seems in vista that they got messed up. its worth a try still think it may be powerdvd8 and ati compatibility though, as 8 is not as good as 7.3 for me with certain dvds.
is it that you cant select ati hardware in configuration or is it blanked out.

PDVD 8 was the only program that would not accelerate. 7.3 and TMT worked just fine. I even tried a fresh Vista install with no other programs loaded. I can select it in configuration but PDVD disables it on playback of HDM.