I know there are many who are defending Maleth and P&O (lengthy thread on TA). Yes Maleth was probably the only option and we all know delays happen with airlines, but P&O would have been well aware of the standard of the planes/service, their lack of resources and contingency for when things go wrong.
Somebody mentioned the contract with Maleth was signed last March, months before passengers were informed in September/October. So they should have given passengers options rather than just drop the change on them and to be told they'll lose their deposits/cruise if they cancel.
As the problems and issues continue, I am amazed that P&O are not making sure that communication is being kept up between them and the airline so that passengers can be well informed.