I see that the Looker community has already shared praise with the Product team and Developers for this feature, I am late to the party but first let me echo that praise! This is definitely a step in right direction for keeping data analytics within the Looker environment and avoiding that painful exercise of exporting 2 Looker Explore results into Excel just to create a chart with 2 series. Bravo!!
I have some feedback that doesn't look like it has been shared yet:
(1) Creating Merged Results - Opportunity to make prototyping quicker?
If I have Explore 1 prepared in one tab, and Explore 2 prepared in another tab (these could be explores that I saved from earlier, just now created, or maybe a colleague sent me), then depending how complex each of those explores are, sometimes I'm finding it slow to merge those results.
I have to choose which will be the "Primary", (let's say I pick Explore 1) and then I have to re-generate Explore 2 through the UI, which I will do by switching back and forth between tabs and mimicking which filters are applied and which fields are selected.
For creating dashboard elements and complicated datasets that require some thought, this isn't so onerous, but it slows things down when you are doing on-the-fly adhoc analysis and you just want to combine two existing visualizations or tables into the same dataset.
I have no idea how complicated this would be to engineer, but if I could paste an explore URL instead of rebuilding the second explore, that would be
(2) Sharing Merged Results
Lots of people have asked about adding merged results to dashboards and downloading the results, but is there any opportunity to give some users permission to create merged results, and give others the ability just to view the results? I've confirmed that users who are not in the named Beta group get a 404 error when I share the URL with them -- until the results can be shared, this feature loses a lot of it's power. Understood that days in Beta may be numbered, so maybe this will be addressed then.