Several of us over on the TLF have outlined our reservations about the proposal to allocate a block of the Advanced Wireless Services (AWS) spectrum for a free, nationwide wireless service. (Here's a filing I signed on to that critiques the portion of the plan that requires censorship of the entire band once allocated).
But, strictly from an economic perspective, this is the best overview and critique of the plan I have seen so far: "The Static and Dynamic Inefficiency of Abandoning Unrestricted Auctions for Spectrum," by Bob Hahn, Allan Ingraham, Greg Sidak, and Hal Singer. It's a response to a paper favoring the M2Z plan that was penned by Simon Wilkie of USC, who also formerly served as the Chief Economist of the FCC. (Wilkie's work on behalf of M2Z can be found on the M2Z site here). It's a good debate and I encourage you to look at both papers if you are interested in this issue.