nickd: @graemeh: Could you explain a bit more? It was my understanding that CGA supersedes the conditions of the warranty, or am I just getting the wrong end of the stick?
You are right, the CGA sets a minimum standard that can't be contracted out of for consumer sales.
The warranty can provide benefits that exceed those under the CGA (e.g. courier pickup and return of faulty equipment rather than making you bring it in and collect it).
My only objection to what you said was the bit relating to a warranty repair always including labour. It depends on the warranty.
Let's imagine a situation where the crack is only cosmetic. If this happens after 3 years (or even after 1) you may have trouble getting this fixed under the CGA but may be easy to fix under warranty.
If the crack makes the machine unusable then it would be covered by the CGA even well after the original warranty expired.
I hope I've made more sense this time around.