Have you implemented an analytics tool like Looker/ Tableau? Has it been successful? What drove the success/ failure? 

We have implemented Tableau to support Data Visualization using disparate sources of data. Its main success was the ease of development of the visualization graphs and ability to connect easily to on premise databases. We are a SAP and Salesforce shop and are also investigating SAP Analytics cloud as an alternative, if the licensing costs become too prohibitive

We have used Tableau, and I would consider it a success.  We offered training internally quite a bit.  Many applications we deploy we underestimate learning curve and training requirements.  This time, the project team made more training available and also recorded a lot of quick tip videos that help people get up to speed quickly

Yes it was success for helping to gather and pull metrics via reports. We then used those reports to prioritize work and effect change across the org.

I attempted to implement it for engineering graphical representation purposes (generating report quality plans) in my last position, however, it didn't seem to be tailored for that purpose. My biggest issue was customizing the call-outs with text and graphics to suite my use. 

Tableau has been successful.

Key has been access to data, training, and awareness of the tool. We also made it usable by business as well as IT teams for report / functional development to drive adoption and usage.