Can Drupal play with WordPress?

We are thinking of taking a site running drupal that has under a thousand registered users and somehow incorporating wordpress. This is because users of our site have many problems figuring out how to blog and such. On the back-end drupal seems to keep randomly breaking. Should we switch to wordpress?

Is there a way to have wrodpress play nicely with drupal or a way to convert the drupal users accounts to wordpress?

How good is WP at handling a large amount of users?