I'm a little worried about what they did with DOS pattern matching. I thought it was just short of *nix regular expressions without being too *nix-y, which is what I fear they have turned it into. I suppose this isn't THAT bad, but the old pattern matching was so elegant.
I doubt much has been done to it - some scripts rely on the more advanced features, and ASL requesters are commonly called with ~(.info|.backdrop) as the default pattern filter. If anything has been done, it would have been expanded, otherwise you risk compatibility.
Whoever mentioned ARexx: there were some small updates done for OS3.5/9 but I'm not entirely sure what they entailed.
Chris