"Powerful, free analytics with support for a wide range of platforms. "
What do you like best?
Piwik installs rapidly, configures easily, and presents its data in a form which is useful for execs and admins alike. I set up Piwik to email daily reports to my CEOs, and that has saved me significant time which I formerly spent interpreting and explaining previously cryptic traffic analysis reports. I use a single Piwik instance to monitor several clients' sites, so it's saved time from an administrative standpoint as well as a site development one.
What do you dislike?
Very little. It's great software.
The Drupal e-commerce extensions are currently not working for me on an older instance of Drupal, but several other modules and, indeed, the Drupal 6 core, are EOL, so I am not inclined to attribute that issue to Piwik developers.
Recommendations to others considering the product
Piwik is simple to install, and free. I'd recommend installing it on a spare server and trying it out, I believe it compares favorably to many paid offerings.
What business problems are you solving with the product? What benefits have you realized?
Piwik's multiple site support has saved significant time, where I formerly had to gather reports from multiple client sites, I now need only check Piwik's single dashboard. Piwik's digest reports are an excellent time-saving feature as well, and are self-explanatory enough for tech-illiterate execs.