Who doesn't like free? Of course as the age old adage goes, you get what you pay for and Piwik is no different. Piwik is an analytical platform for log analysis and real time (semi) user tracking via web service calls. All in all the product is decent. We are running a local version of their software and performing log analysis only.
We (meaning me) ran into problems during a few different stages of implementation. I posted 3 different times to their forum with only crickets as a response. One topic was viewed 138 times and the others around 50ish. Not a lot, but hey someone's looking. There weren't even any responses from that one jerk who says, "I have no idea, man" or the other jerk that says "just RTFM" or the jerk that says "I'm not going to do your schoolwork for you" or the last jerk that is obviously from the java forums who says "if you are too stupid to figure it out I can't help you" (you know who you are!).
There is one guy, Matthieu Aubry (the creator of Piwik) who does make great efforts to answer questions, but he appears to be just one guy (or ARE YOU?!?!?!). I do not fault him in any way and as a developer who also supports users I understand the lack of time he has to do both.
Piwik does have paid support contracts that will solve the world's problems, but it is rather expensive. For the little guy you are SOL. Piwik has a stackoverflow section, but that too is sparsely answered. In the end, I spent way too many hours troubleshooting and trying to figure things out, but hey you get what you pay for.