Glad the issue could be replicated. @elangley: thanks for submitting a trac ticket. I’m definitely interested in having this issue fixed. And thx as well for the advice on the BuddyPress Import plugin, will try it.
Installed a plugin for users to login with their e-mail address or their username (which they typically forget) Plugin is WP Email Login: *Allows you to log into WordPress using your email address instead of a(nother) username.* Can be found at http://wordpress.org/plugins/wp-email-login/