Tony Chartrand-Burke has written a blog post on the Secret Mark session at SBL. Though he claims to "remain an agnostic" on the matter, I think it's apparent from his comments that he considers the dissenting voices' arguments less than compelling. He states:
The two main writers against the authenticity of the text, Carlson and Jeffery, are not biblical scholars. Their arguments are not based on the methodology used by biblical scholars.
I've not read Jeffery's book, but as far as Carlson goes - this is poppycock. This seems to be ivory tower snobbery and not really dealing with the issue at hand. Arguments stand or fall based upon the evidence, not someone's supposed credentials. Secondly, Carlson didn't decide to go do doctoral work in New Testament on a lark - it wasn't as if he, one day in the courtroom (I know he wasn't a trial lawyer), thought, "You know what? I really fancy the New Testament. I'll see you folks later" and walked into Duke. As Mark Goodacre points out, Carlson had already published in New Testament Studies.
Third - both Carlson's NTS article and his book utilize "methodology used by biblical scholars." I've had the chance to talk with Carlson at length about things related to the Synoptic Problem and he was incredibly well-informed. I think pointing out that he's a lawyer in order to derail any of his arguments is a weak line to take - but I suppose we should just leave the logic up to the lawyers.
I read over Jeffery's response to Scott Brown's review of his book. Anyone who cites Schillebeeckx, Bouyer, Joel Marcus, and April DeConick is very very okay in my book.