I wonder how much effort they've put into optimisation? Small gains (1-2% rather than order of magnitudes) for these guys obviously mean a lot more than for any bedroom operation.
OTOH, every day earlier that you start mining is also worth money. This favors more conservative chip design. Now that conservative 28 nm ASICs are available, they may switch focus to optimizing the design.
That occurred to me while writing the comment, but I assume there are other factors which could be worth monitoring and improving, for example network topologies or even cooling methods.