Ok, PauPress 1.0.9 probably deserves 4 stars due to its lack of some features you'd expect from a full-fledged CRM. It's still a relatively new plugin.
That said, it is currently the best CRM integrated in WordPress I found - I think I tried them all in the past two weeks. More features and more actively developed. And their support is stellar, they genuinely make an effort to help users.
I ended up buying the Pro version. For 45$ for 1 year of updates with their Pro features (the Pro version will continue to work even if you don't pay for another year). It appears to be well worth.