Analytics tools, with file import capability

The issue we are facing is as follows: we are providing rich internet applications to corporate clients. As we wanted to obtain feedback on application usage patterns and our clients frowned upon integrating our applications with 3rd party tools such as Google Analytics, we finally had to resort to implementing an "in app" logger, which tracks the basic actions such as which screens the users access, which menus and icons they click, etc. The logger can produce the output in form of XLS, CSV or TXT files.

The question is: anyone knows of a simple analytics tool, into which the XLS / CSV / TXT files can be imported and analyzed? We would like to obtain an overview of the typical: number of sessions per day, average session duration, views / menus / icons must frequently accessed, etc.

Of course we could use Excel and create the analytical formulas, but that might take a lot of work and we would prefer to use something that's already tried and tested.