Following this thread, Xavi had made the Rdata files and caches always "per user", which pretty much disables caching for sites where multiple users should see the same thing.
I have now added an option cachestrategy which allows to choose per user or everybody sees the same for each plugin. Plus a no cache choice which might be useful when trying to write/edit/fix/test the R script.
'options' => array(
array('text' => tra("One cache per plugin"), 'value' => 'one'),
array('text' => tra("One cache per plugin per user"), 'value' => 'peruser'),
array('text' => tra("No caching: Ignore and replace existing cache, if any"), 'value' => 'nocache'),