Apparently Cumulus will not work due to some problem with Tagadelic and Drupal versions above 7.8. See:

https://github.com/berkes/tagadelic/issues/7
http://drupal.org/node/1435238
and finally a possible solution: http://drupal.org/node/1435238#comment-5788172

Perhaps it might be useful to note this on the project page just as a courtesy/warning. So that people don't waste time installing if they can't/wont patch code?