This from the CX website...
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Cabin baggage reminder
For added safety (to you and our cabin crew) and convenience, all travellers seated in the upper deck of our B747s are required to make use of the overhead lockers and side-wall compartments to store your luggage. We apologise the upper cloakroom is no longer available for use due to new, improved safety measures.</font>
This is potentially something of a problem - neither the overhead bins nor the side lockers are anywhere near big enough to store a standard size (22x14x9inch) carry-on bag. So what is the option? Stow the bag somewhere downstairs where you have no idea what might happen to it during the 12 hour flight if you are upstairs, or take a downstairs seat.
This changes significantly the attractiveness of the upper deck in my view.