Migrate from WordPress (with buddypress plugin)
I did a Wordpress import this summer into a Drupal 6 system.  While I ended up doing a manual import for a variety of reasons, a decent amount of my code was based on Wordpress Import.

This module has been suplamented by Wordpress Migrate which uses the Migrate framework.  Since you mentioned Drupal 7, this approach would be worth exploring.

Both of these use the WXR format, so you are likely to lose less data than with other methods, and you can generate the backup file right from the WP admin interface.

Personally, I would take a backup of your site (like with Backup and Migrate), and try out Wordpress Migrate before trying to use Feeds.

Keep in mind that Wordpress RSS and WXR files may not always be valid XML, so you may run into parsing issues.  I have had problems because of WP plugins that add embed code or &lt;script&gt; blocks directly into the post/page, and then WP doesn't wrap everything properly in a CDATA section.

It is also worth noting that you may end up losing any markup that would be the result of short-tags in the post/page body, and just import the sort-tag.