have you seen http://www.tableausoftware.com

I see tableau doesnt support google docs as a datasource, but still, your software seems pretty close to what they offer

the BI (business intelligence) arena have man big players Cognos, MS, SAS .... so watch out

my suggestion is you might wonna consider supporting more datasource other than google docs

most data that ppl seriously work on, is usually stored into a db, of course people do use spreadsheets sometimes as an export format for this data for adhoc querying but nevertheless you do need to support more datasources

so my suggestions would be, watch tableau software demos, add support to more datasource, make it open source and good luck .. there are so many way to go :)