I think it is a pretty well designed piece. It allows you to fit a reservoir and two pumps into two 5 1/4" bays. Granted it is a parallel setup for the two loops with shared reservoir, but I believe if you have enough cooling for each loops load, performance should be similar to what you would have for two loops in series. Another benefit is that you can start with just one pump/one loop, and add the second pump and hardware later. It gives your system room to grow.
I am in the process of building a new water cooled PC based on a Coolermaster HAF X case with a 360 mm and a 240 mm radiator setup inside. It looks like this is the answer to my prayers as far as keeping everything neat and tide. I will order be ordering one at the end of the month when I get paid.
Note: This reservoir/pump setup has been discussed in detail in this thread:
New Koolance *Dual D-5* Bay Reservoir! (RP-450X2) - XtremeSystems Forums