Agreed, in this one a better opponent would have been Hitchens, Harris, Dawkins or even Barker. I've not read the Skeptic magazine. I don't think we can get it here in the UK. Shermer does have a brilliant mind but it is more better suited to the scientific arena.
I think Hitchens, and Harris can cover both Christianity and Islam very well--Hitchens being the better of the two in my opinion. But, Barker I think should only deal with Christianity since that's where he is most knowledgeable in. Shermer and Dawkins I think should deal with scientific debates. Again, that's just what I think based what I've heard from Hitchens, Harris, Dawkins, Barker and Shermer.
Now that would be a great debate. I would also like him to debate Zakir "pants too short" Naik. Other debates I want to see is with people like Hamza Yusuf and Abdal Hakim Murad.
I like Hamza Yusuf over Naik--particualrly because Naik doesn't know anything and he's a hate monger. Hamza is a lighter version of the same shit Naik spits out.