Version 2.8 of Plugin throws lots of errors, slowing the site to a crawl.
I've downrevved to v2.73 of plugin and it seems to be working OK again
In both cases, the plugin is producing and storing data about users.
Errors all similar to this
[24-Sep-2010 06:22:43] WordPress database error Duplicate entry '2010-09-23 23:22:43-guest-184.108.40.206' for key 1 for query INSERT INTO
referral) VALUES ('guest','0','Guest','220.127.116.11','Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.62 Safari/534.3','Morgan Hill Soccer Complex Field Map','/2009/11/morgan-hill-soccer-complex-field-map/','http://sporting97green.com/2009/11/morgan-hill-soccer-complex-field-map/') made by do_action, call_user_func_array, UserOnline_Core->ajax, UserOnline_Core->record