Ror with MongoDB problems and questions

Hi
Ok what i want to do is work with MongoDB using standard ActiveRecord
methods like Model.all Model.find and so on but whithout ActiveRecord
itself.
First to notice Ror using database.yml where we create connection config
like
define:
adapter
database
login
password
socket

ok for mongodb we have no adapter and then we cann't use database.yml at
all.
We can create own mongodb.yml where we can define:
server
port
database
how ror knows wich config to use(database.yml or mongodb.yml) i don't
know.

and then define that in mongo_config.rb in initialize folder. Like
MongoMapper.connection =
MongoMapper.database =

at railscasts.com Ryan suggest only adding MongoMapper.database = "base"
in mmongo_config.rb ( gem 'mongo_mapper' required in Gemfile).

After all you make model like this
class Person
include MongoMapper::Document
key:name
key:lname

it should use mongo_mapper but it fails.
It doesn't work. At least with Rails 3beta and 1.9.1. Because it still
using ActiveRecord some how and database.yml accordingly. And server
doesn't work and console.
So i didn't find a method to switch off ActiveRecord easily ( earlier it
can be done by config.frameworks -= {:active_record} and it doesn't work
for rails 3.)

Ok what to do with this ? Tell me your experience.

And for Ror core team it would be wise to implement switching on off
gems like ActiveRecord for application and (or) make adapter for
document-based DB's because popularity for this kind of DB's now is
growing pretty fast. And it will be easy to use mongodb adapter instead
of making custom implementations.

ok i guess i fixed problem
I installed "devise" - auth manager and it works only with active_record
and mongoid and doesn't support mongo_mapper so far.
So in config was active_record by default.