Nicholas Carr's Rough Type blog jokes about Microsoft's container data centers being a trailer park. But, he appends his blog later quoting the searchdatacenter interview with Mike Manos and Christian Belady.
UPDATE: There's more on the data center philosophy of the 'Soft Boys in this interview with Manos and one of his colleagues. On the attraction of containers: "One of the things we like about them is we can take a bunch of servers and look at the output of that box and look at the power it draws. At the end of the day, we can determine, 'What is the IT productivity of that unit? How many search queries were executed per box? How many emails sent or stored?' You can get into some really interesting metrics. A lot of people say you can't look at the productivity of a data center, but if you compartmentalize it - not as small as the server level, but at some chunk in between - you can measure productivity."
This is one advantage Microsoft will gain from going down the path of containers in that it will be easy for them to use the containers as a unit of measure for PUE and compute capability metrics. As they update the hardware in a container, they will be able to make comparisons between versions. They will now have 220 possible mini data centers (containers) to experiment on what are the right combinations - storage, memory, processors (AMD/intel), SSD, network configurations, power systems, etc. This is going to let them experiment and have a standard unit of comparison. This is innovative.