Number of ancient one cards, spells, and allies all matches the original, so probably not much change to the content there either (though there might be a few clarifications, I suppose, and finally fixing the wording on the "Triune Mask" encounter...)
Exhibit encounters deck seems a great way to deal with the "you never get an exhibit item with all the expansions" dilution problem. It sounds like this is the way that Miskatonic Horror will add more opportunities to get an exhibit into the game, too.
Sounds like the free herald is coming nicely printed in this box
Patrolled neighbourhoods might be a replacement for Barred, bringing the great taste of Innsmouth to Arkham. But at least the Arkham jail doesn't have Shoggoths.
One the one hand, it all sounds like a great improvement on the original. On the other hand, I already own CotDP and most of this isn't new.