+1 for having the dimension name in the tooltip. Otherwise, I can see the outliers but don't know what they are! Plus I would want to be able to drill from that dimension from the scatter plot in order to get more information about it!
My scenario is - I am looking at communications sent by the marketing team, and wondering on which device they are getting read - would like to scatter the number read on the mobile v. desktop then hover over the data point and see which email it is. Obviously, if more people are reading it on mobile I want to know that. And then click on the data point to see more information about this communication.