I think yes as an engineering achievement, but no as a device for carrying 1500 chavs to Benidorm.
I'd go with yes for both so long as they didn't come back!
To be honest, no I don't think she should be built. It is only a matter of time before a cruise ship goes hurtling to the bottom and the bigger these ships get the more people are going to be killed when it happens.
Yes safety standards are high, but it is impossible to prevent every accident, and by the law of averages one of these days one of the accidents will be major, as these ships are getting larger and larger they are also becoming technically more and more complex, combined with ever dropping standards in training for seafarers means that accidents become more and more likely, the scale of any major incident becomes larger and larger and the crew will be less and less able to deal with one when it happens.
Apart from that I think these very large crowd carriers also loose something that was special about cruising in the days of smaller more intimate ships.