I hope everything you say about what makes the game repayable turns out to be true. It sounds like a real actual video game!
I haven't played it yet myself, but that's what the couple people who played it here said, what my friend said, what others around the internet are saying, and what the first couple of reviews said (one was horribly translated by Google though as the site is Arabic). To detail it completely, this is what I've pulled from all the impressions of people who have played it and beat it:
-The game is fairly easy on the lower difficulties, but actually fairly challenging on the harder ones.
-The scoring system the game uses is a lot of fun, having a good balance of various things you can do in a stage to affect it, from collecting medals and defeating zombies, to doing sub-missions in stages, time, execution of special moves successfully, and other contributors.
-All of these can be used for a few score modes that get unlocked, which there are a total of three, based on time, score, and medal collecting.
-The high score mode of levels aren't the same as the story mode version and have been reported to include new enemies, an increase in enemies, or in some cases changed stage layout.
-The game has at least two different endings (this is based off of the game's achievements and reports, but there is a possibility of a third ending I hear but cannot confirm)
-The game has unlockable difficulty modes, including a perma-death mode where you have to get through the whole game with one life.
-Not including the pre-order costumes, there are 19 costumes you can unlock in the game outside of the default.
-You can buy music to play while you play stages in the shop.
-You can also buy artwork from the shop.
-Enemy AI changing based on your difficulty setting has been confirmed
-Harder enemies appearing on harder difficulties also has been confirmed, with a few enemies exclusive to the harder difficulties.
-If it isn't already evident, this game has a stage select option (they obviously heard the complaints from Shadows of the Damned)
-Juliet has a 'level' that you upgrade over the course of playing. I actually don't know if this level applies to the score modes, though.
-You can buy new moves for Juliet.
-I don't have a confirm on this, but I've heard that unlike Shadows of the Damned where the bosses only got more health when on harder difficulties, on harder difficulties in this game they get more aggressive and sometimes have new moves or are prone to use their deadlier moves more often.
There might be some things I'm forgetting, but that's about what I remember.
Has there been any word whether the pre-order DLC will go up for sale eventually? I really want to get the Best Buy costumes.
No word yet, the developers said they were exclusive to pre-order bonuses, but I'd be surprised if Warner didn't put them up for purchase.