bp_get_signup_username_value()

	function bp_get_signup_username_value() {
		$value = '';

		// grab the nickname field first
		$nickname_field = 'field_' . bp_xprofile_nickname_field_id();
		if ( isset( $_POST[ $nickname_field ] ) ) {
			$value = $_POST[ $nickname_field ];
		}
		// fallback to grab the username
		else if ( isset( $_POST['signup_username'] ) ) {
			$value = $_POST['signup_username'];
		}

		/**
		 * Filters the username submitted during signup.
		 *
		 * @since BuddyPress 1.1.0
		 *
		 * @param string $value Username submitted during signup.
		 */
		return apply_filters( 'bp_get_signup_username_value', $value );
	}