[jyothi]

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.