When visitors come to your site, you want to know (i) what search term or link they came from; (ii) which Country they came from; (iii) did they browse any other pages, (iv) how long did they stay on the site.
This information is very valuable. If people are repeatedly coming to your site in search of a keyword, you know you have to write more posts with that keyword in focus.
WordPress Plugins to track visitors:
The wordpress plugin space is dominated by about three plugins:
Two others that do the same work are StatPress Reloaded and StatPress Visitors which are variants of StatPress.
My experience is that the WordPress visitor traffic plugins get affected by cache plugins like “Quick Cache”, “WP Cache”, WP Total Cache” etc. While you will see statistics, it is not the entire list. I suspect, it only catches the information whilst the cache is being refreshed. In fact, on the Wassup page, there is a clear declaration that “WassUp is incompatible with page-based caching plugins such as “WP Super-Cache“.
Best Alternative To Track Visitor Traffic:
My favourite tool is “tracewatch“, a php programme that works very well. You have to create a MySQL database, download the tracewatch files, enter your database info in the config file, upload it to the server, run the installer and put two lines of code on the pages you want to track (index.php, single.php & page.php) and you are done.
There’s a wealth of valuable information that tracewatch can provide you which you can then use to provide a better experience to your visitors.
My own experience is that once you try tracewatch to track visitors, the other wordpress plugins will seem amateurish in comparision.