I’ve been having some issues using the

- (NSManagedObjectModel *)managedObjectModel
function. First it didn't load well, but Marcus Zarra helped me out there on Stack Overflow. The funny thing was of course that up until now, it'd worked great on the phone but not the simulator. That solved, it stopped working on my phone, but I was working so much in the simulator I didn't pay a lot of attention to it.
Anyway, today I wanted to have that figured out, and I came across this great post by Jeff Lamarche, and while it didn't explain to me why I had multiple versions on my phone but not my simulator, even after I had wiped the application and application data completely, it allowed me to load the correct model. So now everything is running smoothly and the app is coming along great.
If you've been having the same kinds of issues, I hope these links help you as much as they did me.