I love this plugin. Just like most WordPress sites that allow user registration, I get hit with tons of spam. Askimet is excellent at clearing out the spam, but your plugin is the only quick and efficient way (that I know of...) to clear out all the spam accounts.
If you ever have any-time to work on a future update, please consider adding compatibility with BuddyPress to the todo list.
Right now, the plugin still works if you use BuddyPress, however, it leaves some remnant user information behind. For example, BuddyPress has an "activity" page that will show things like new user registrations, new forum posts, new comments, etc... When deleting with user spam remover, this activity page will still display the "new user registrations" message for users that no longer exist.
When you delete a user via BuddyPress all of this is removed. While I'm no expert on how this works, it may be possible to detect if a site is using BuddyPress, and if so, call or copy/paste the BuddyPress delete function into your plugin.
I'm not certain if it leaves anything else behind, or if it's just information that has been added to the activity log. For example, BuddyPress also adds additional profile fields associated with users.