Is the property very substantially completed?
I think in todays climate, I would advise clients if at all possible and if property is at a sufficiently advanced stage to snag before contracts but also, again, just before completion.
If property is substantially complete, and snagged before signing contracts and if major issues become apparent, the purchaser can pull out with no loss and no worries about builder trying to argue the toss. It seems that some people are having difficulties with poor build quality and it is an issue after contracts but before completion as to who is the arbiter of what is acceptable/unacceptable.
mf