You can use google Analytics, just need to set the username in customvar, here is an example.
Using jquery, jquery cookie plugin, jquery spservices.. In Google Analytics you can use the customvar1 in custom reports..
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-XXXXXXXX-1']);
_gaq.push(['_setDomainName', 'XXXXXXXXXXXX.com']);
// Get Username, try from session cookie first
var savedName = $.cookie("svName");
if ((savedName==null)||(savedName==""))
{
savedName = $().SPServices.SPGetCurrentUser({fieldName: "Name",async:false,debug: false);
$.cookie("svName",savedName, { path: '/' });
}
// Set Google Analytics Custom Var
_gaq.push(['_deleteCustomVar', 1]);
_gaq.push(['_setCustomVar',
1, // This custom var is set to slot #1. Required parameter.
'SPUser', // The top-level name for your online content categories. Required parameter.
savedName,3 // Sets the value of "SPUser" Required parameter.
]);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
Regards
Alvaro