Can you please stop this Neil? I know your upset that your lens was a dud but to seriously believe that 9/10 of these lenses are similarly borked is plainly ridiculous. The number of happy users in this thread alone disporves that statistic.
While 9/10 is obviously a stupid figure I would be interested in the true amount.
What is interesting is the number of people that have to go through several copies to get a good one. This is what makes me believe the QC is fairly poor. If someone gets a single bad lens then they will report it online, if someone gets a good lens they wont report online, hence it makes an artificially high number of complaints. E.g. maybe only 1% are bad but given the sales figures that may eqate to a fair amount of complaints. However, if someone goes through 2 or 3 copies then this puts a worrying estimate on the number of failures, which must surely be higher than 1%. E.g., if someone goes through 2 to 3 copies then that is a 66-75% failure rate for them personally. These could be unlucky people (1 in 10,000 or 1 in 1 million for a run of 2 or 3 bad copies with a base failure rate of 1%) if many people experience the same then it is not bad luck but simply poor QC.
I also wonder how many people buy the lens without really checking for calibration or alignment issues and simply accept the performance of the lens? Being a budget lens means lots of inexperienced people will buy it and without knowing better will accept small amounts of softness or focus issues, especially if their technical skills are low anyway. People who lay down the cash for Nikon are probably fairly determined to get a good lens after paying all that money!