So few do... Unfortunately, as you are learning, you have bought a camera which uses the most demanding of all video formats, namely AVCHD. I too have a Quad, and if you read posts over the last few days, you will see that a lot of people with less powerful computers are having lots of problems editing and even playing back AVCHD smoothly. Your Quad should be able to do so.
That being said, what aspect of it are you talking about -- only the preview in VS being slow? Or is there choppy playback in other programs as well? If it is only in VS, then I would not get too upset. I find that even my HDV high def format plays back somewhat choppily on the Quad in Project playback mode and that's a somewhat easier format to deal with than AVCHD. But I have had long experience of the VS preview screen going back to VS7, and these days treat it only as a way of seeing how my edits look, even if it is looks as though it is jumping frame to frame or is in slow motion. The real test is to complete the editing and either produce a new AVCHD of the whole project as edited, or else burn it to a disc (Blu-Ray or hybrid DVD which accepts AVCHD in high def format but will only play back on a Blu-Ray rated player). Then I find playback on the Quad to be smooth as silk...
VS 11+ without the 6 November 2007 patch and the 8 November Power Pack cannot handle AVCHD, by the way. And FYI VS11.5+ is really only VS11+ with those two updates applied.
You might also want to consider using SmartProxy in VS11.5+. In effect, it creates SD versions of your HD files, and the edits are applied to the SD proxies in real time. They should also play back in preview smoothly. And then when you have finished, the edits are applied (rather slowly) to the HD originals.
