Hardmac has pics and a report on one user whose MacBook is starting to come apart at the seams. The top of user Tristan’s eight day old MacBook was separating from the base, leaving a gap between the two pieces of plastic. When reported to Apple, the company agreed to replace the machine for him so they could figure out what the issue was.
Given the common quality assurance problems we’ve seen with revision A products from Apple, the MacBook experience seems to have been overwhelmingly positive. I’ve seen very few problems reported, and the ones that have come up (the mythical black finish scratching, for example) seem to have been isolated incidents. My experience has been very good overall. If I had any things I’d want Apple to fix about the MacBook, they’d be: 1) lower the heat output (I can certainly live with it, but obviously, lower would be better) and 2) smooth out the front edges of the case, below where my wrists lie. They’re sharp enough that I keep expecting to see splashes of red across the front of the computer from the repeated sawing at my arms. Other than that, I’m complaint free at the moment.
As long as MacBooks are made of plastic they'll always be a little more flimsy than a PowerBook/MacBook Pro. My sister's iBook is a little crooked. The screen doesn't sit completely flat anymore when closed; the battery sits a little lower to the surface which the machine sits on. Not a problem, just kind of scary when it first starts happening.
Coming apart from the seems is obviously much worse, but I'm just saying it would be much more expected to happen to a MacBook than a Pro