Hi David, thanks for responding. I tested fglrx just now and every time I launched VLC with audio, or in this case even Totem with audio, the X session went boom right before any sound came out. So if you meant "does it work without tsched=0 when using fglrx", I guess the answer is no. I'll attach the X log, although this crash is probably unrelated to this report. (I only use the free drivers myself so I won't bother to report this separately. It was pretty consistent and should be easily reproducible though.)
I didn't know whether the radeon.audio=1 kernel parameter matters when fglrx is in use, so I tried both with it and without it, with the same result (X crash).
The only thing audiowise that didn't crash the session was PA's speaker test (from the audio settings). It didn't make any sound either though.
Luckily, enabling Radeon audio in the kernel hasn't given me any problems on this setup, at least such that I could link to it. I do have Bug #917668 filed in, but it'll have to reoccur to get more data to see if that's connected.