I did the similar thing but with nodejs to collect and process the events and Postgresql JSONB for storing the events .... i see the advantage on this approach is that i dont need to do much for structuring the data in node as i am just dumping this unstructured data directly into JSONB column , but i believe in your case you are structuring it first in Django and then storing it in hstore .. 
I totally agree with you about the Visualisation .. thats the hard part .. in my case i have totally unstructured events but still i managed to use a simple node app to give me the data back by querying JSONB .. was it easy to query HSTORE??