Former Solicitor General Paul Clement, now a partner at King & Spalding, will argue on behalf of the plaintiff-appellees (the states, the NFIB, and the two private individuals) in Florida v. HHS at the Eleventh Circuit. This AP story has the news (sort of, at least, identifying him as "Peter Clement").
Clement is a terrific oral advocate (most recently arguing at the Supreme Court on behalf of the petitioner in Bond v. United States February 22, audio here). He also memorably faced off with former Solicitor General Seth Waxman in Boumediene v. Bush (audio here)--in my humble opinion, one of the best argued cases in the modern history of the Court.
There are two potential implications here: (1) the United States is in for a real run for its money, if that was not already clear; and (2) this makes it marginally more likely that Florida v. HHS is the ACA case on which the Supreme Court grants cert.