While the article stress the importance of understanding your power requirements on the server side you also need to be very cognizant of the power restrictions in your colo contract. Often times power draws will be your biggest limiting factor and it is very easy to buy a rack and fill it with equipment that surpasses your max allotted power draw. Depending on your host your only solution may be to buy additional racks to spread out your load even though you don't need the physical space.

Another power gotcha comes with the redundant circuits provided. For example if you are allocated 15Amps total that usually means total across both circuits not 15Amps per circuit.