I don't see a drop in build quality with Apples x86 machines. They seem to be putting just as much attention to detail now as they did in the PPC era. It's not like they pulled a Packard Bell and started using recycled parts or lowered their standards for rolling out PCBs.
For a time there was a massive, obvious drop in quality with their MacBook hardware. The first Intel MacBook, which took over from the iBook, had all sorts of issues. I personally know of 3 which suffer from cracked plastic around the keyboard cover and failure of the trackpad button, two of these which have had failed wireless cards, two have also had battery failures, and one has had an optical drive failure. None of these had what I would consider atypical use, and my previous-gen G4 iBook is rock solid and outlasting them all in every department (except ability to use Flash, but that's another story). They're not alone either, the internet's full of these stories, far more than the usual volume of complaints you would find on another machine.
Now, those issues were fixed for the newer MacBook with the all-in-one plastic body, and the Pros never had those issues, but at the time it gave the distinct impression of a major drop in quality.
