Over at Balkinization, Marty Lederman and Cass Sunstein have been mulling the Hamdan decision's implications for the legality of the NSA conter-terrorism surveillance program. While they don't agree across the board, they concur (as do others) that Hamdan undermines the most plausible arguments in support of the NSA's activities. Here are the links:

Lederman's initial post;

Sunstein's response;

Lederman's reply;

Sunstein's surreply.