Hi Hansi,
The proceedings are great. They're really, really cheap too, at least if you're a SIGGRAPH member. It's about $70 US for the full conference proceedings package, and $25 or so to join SIGGRAPH ( that's for the SIGGRAPH membership, not the full ACM one ).
I reckon if you were keen the conference DVDs ( not the ones which come with the proceedings ) would be a good buy. They record all the sessions. I've always thought they were a bit expensive, but they have some big advantages. For one thing, you can skip over the boring bits :-). You are also less likely to fall asleep than you are when it's the 3rd day of the conference and you're sitting in a dark, warm room listening to someone with a monotonous voice. Even if you're at the conference it can often be hard to see all the things you want.
Regards,
Jo