Played a bit longer today, and really began to feel this game. It's slick, and it's a bunch of fun. They took all the mechanics from Arkham Asylum, and just beefed them up a little bit, and then asked all the good design questions: "what if you only have a limited amount of time?" and "what if you should beat up everyone EXCEPT one guy?" and other means of just tweaking their basic mechanic a little and opening up variations.
In Asylum, I think the guys with knives had to be cape-stunned before you could hit them, right? I am really enjoying the intuitive knife-dodge, and the satisfying payoff of knife-takedowns.
Anyway, I made it all the way through the museum and its inhabitants, back out to chase the "ninjas" and then took a side-trip to the Church, just so I could start opening up the Riddler content, which I'd been finding all over but had no means of "solving." (Game won't let you scan anything until you've spoken with the Riddler at least once (which is kind of lame)).
Good game is good. Saints is going to distract me from this, I'm sure, but it will be a near thing.