Like Professor Kerr, I thought this case was quite close. Could go either way. The mark of a superb justice is one who can cogently explain the reasons for their decision (in a dissent, no less) in a case in which rational persons might differ on the result. Here, Judge Roberts performed exceptionally.
UPDATE: Haha. Althouse brings us the start of Judge Roberts' opinion in Consumers Energy Company v. Federal Energy Commission, 367 F.3d 915 (2004):
It was a close thing, but Benedict Arnold's bold plan to capture Canada for the Revolution fell short at the Battle of Quebec in early 1776. As a result, the Federal Energy Regulatory Commission must now decide when affiliates of Canadian utilities -- utilities not subject to FERC jurisdiction -- may sell power at market-based rates in the United States.
Add that one to Roberts' legendary line about "the hapless toad which, for reasons of its own, lives its entire life in California" (I'd give the context, except I've discovered it completely ruins the incredibly poetry of the phrase).