I went ahead and inplemented it in a spike, changing from restful_authentication to authlogic. The only gotcha I found was needing to add the following code
/app/models/user.rb
class User
include MongoMapper::Document
...
def self.quoted_table_name
"users"
end
end
The quoted_table_name was being requested when creating a new user_session, so I added it and everything was great and happy.
Highly recommend.
UPDATE
Once I started using multiple users, the login features stopped working for me. It would log you in if you use the password of the first user, but nothing else mattered.
I switched to this initializer: https://gist.github.com/444888/e8b28196c4f4452a06b89d566a6a245eae1e9d92, which has been nice. I also recommend looking at Devise, which has this straight out of the box for mongomapper.