I'm currently using Jeff Minard's WP-ShortStat plugin.  It's a great statistics plugin that shows recent referrers, browsers, operating systems, pages viewed, search strings, and hits.  It didn't work at first, and I found out that it's not completely compatible with WordPress 2.0.1, but there's a really simple fix:  On line 13, change "if (function_exists('check_admin_referer')) {" to "if (function_exists('user_can_access_admin_page')) {".  That's it.  It works fine after that.