Looker

Looker is incredibly easy to use for a casual user, which most of our users are. As soon as your email is activated, you have access to the product and new users need very little direction to start getting value out of it.

Relative to other BI tools, the advanced charting functionality is somewhat limited, but frankly that's not the main reason we bought Looker. Data scientists can use another tool of their choice, we have Looker for people who aren't data scientists.

very quick deployment, self serve abilities for the business users are very high.
Mediation layer management is very good, it is "Code" based and not setup based so it is very easy to replicate/versioning and find "Hacks" to many needs, and versioning is managed by GIT.
Support is amazing, always available.

Still lacking a little bit on the graphic side, Would really love to have some more buildin dynamic graphs.

It's a great data exploration tool for users who normally would get anxious when given a large dataset in something like Excel. It's generally simple to use and there can be unlimited Viewers (users at the lowest permissions level) through the enterprise product. Data Visualization is essentially done for you and Exploers (users at the second level of permissions) can build new visualizations & turn them into interactive dashboards.

On the Looker platform, Explorers can locate a view (called an Explore) and then are given a list of dimensions and measures they can pull into a table. Users can create new dimensions using calculated fields and then save their views so any users with Viewer permissions (and up) can see what was put together.

With simplicity comes lack of flexibility. More skilled data analysts will want more flexibility than Looker can provide but at the same time you need to have highly skilled Data Analysts to be the Developers (high level of permissions) to set up the data so that less skilled analysts (the users who benefit from Looker most) who are Explorers don't build views that grossly misrepresent the data.

My biggest pet peeve with this software as an Explorer is that you cannot make calculations on the base data...only the data that you pull into your table (called table calculations). That is a major feature that Tableau has that Looker does not have at the Explorer permission level. Of course developers can use LookML (Lookers data language) to create a new column...but a Developer license is more expensive and creating the fields take time and it's something you constantly will need.