My Thoughts on Thoughtspot!

PROS
Tableau is On-Prem. A read against Cloud datawarehouse resource will not efficiently use the power of  warehouse resources unlike Thoughtspot
Complex Operations possible with simple Natural language keywords.Faster Insights
Efficient RLS Row level security
Flexibility with Front end drilldown and less effort with designing the dashboard
Cons
"Single source of truth is our goal. Design is currently NOT in place to support where we want to be. 
With Data meshing ideas floating, this may change our perspective. 
Selling to switch from Tableau to Thoughtspot might be Challenging"
Lack of Flexibility for quick tasks. No access to spreadsheet. Move away from Self Analytics to Technology involvement
Unstructured data direct access. 
Inability to use Custom queries

Longer time to setup. With single source of truth, the process/design can be governed better with tradeoff of losing self- analytics flexibility that Tableau offers.