I've used piwik, it really powers the way you can do in-house analytics. Real time, javascript based tracking - no need to wait for data to accumulate. Plugin model makes it highly flexible and extensible. Module Design is very good.

I wanted something to analyze existing log data and could quickly write a small extension to do that. Creating new views or data points were straight forward too. Could easily integrating a simple external package like statviz.

Wasn't very fast processing data in bulk - 20 minutes to process 200K visits. But this was like a year ago. Ofcourse php, Zend db has its limitations with data processing and if the fact table and aggregate creation is rewritten in perl, C++ or something and done at predefined intervals without doing a running average it can handle fairly large amounts of data I suppose.

I've been using this for a few weeks and it is really solid. It feels nice to have my analytics data on my own server instead of the GOOG's.

Now they only have access to almost all of my data...

Piwik is nice; another open source tool worth looking at is Open Web Analytics, http://www.openwebanalytics.com/. Both have their advantages and are both under active development.

The real power of GA is watching it scale to handle 100mm+ monthly pageviews. Can Piwik do this?

Dealbreaker for me: Piwik cannot do page-specific stats.

Everything else was in Piwik's favor, but I'm going to have to use GA because of this one requirement.

Sounds like there could be a trade-off between using resources on your own server to keep track of these analytics versus just having Google do it. But then maybe it is insignificant.

Anyone has some stats on how much hit on the server it is doing?

Been using it myself since... around 0.2 or so, very satisfied.

The upgrades were painless too, which was a nice surprise - I expected a few hickups during the earlier releases, but found none.

Just wondering: does anyone know of a mere log analysis tool, that would just look at Apache's logs? What data would I miss, compared to Javascript or PHP based tracking?

I'm asking because I'm looking for a non-invasive method, which I could use on old logs if possible.

I used slimstat (w/ PHP) a while back, and it was pretty decent. I wonder how they compare...

An amazing product that I've been following for the last year has reached the 1.0 milestone.

I don't use GA so can't comment on feature parity. Importantly (for me) it has a powerful API, plugin architecture, easy integration, dead easy multi-site configuration.

I can't speak highly enough of this product.