Ken White has looked at the amicus briefs (I think), and explains, as entertainingly as possible, what the current status of the case is:

So: here we are. Mr. Mann has filed a motion to dismiss the appeal on the theory that the denial of an anti-SLAPP statute is not immediately appealable and on the theory that the defendants are all awful haterz who think Waterworld is a feel-good movie. That motion and the Court of Appeals’ order for the parties to brief the issue apparently crossed in the mail. If the District of Columbia Court of Appeals had a docket accessible online, or gave electronic notice of orders, that would not have happened, but since it is 1986 and the District of Columbia is an obscure jurisdiction, it is understandable they do not. National Review et al. has filed response to the order saying they are entitled to an immediate appeal and that, in so many words, Mann is a butthurt censorious twit. Defendants are supported by amicus briefs on the appealability issue from the ACLU, a conglomerate of media companies, and the District of Columbia itself, whose amicus ought to say “lol we suxxors at drafting statutes plz fx k thx bye,” but in fact does not.

Next up, unless it finds another procedural dodge, the Court of Appeals will decide whether the DC Anti-SLAPP statute allows an immediate appeal. If the answer is no, it goes back to trial court for discovery and motions and possibly trial; if the answer is yes, then the Court of Appeals addresses the merits of the anti-SLAPP motions — which, in my opinion, are meritorious.

Obviously, we think so as well.