I like being able to see new daily cases in line (not cumulative) chart. I couldn't figure out how to choose which countries are displayed. Numerically large ones make the shapes of newly growing ones hard to see.
Edit: that was easy--comma separated country names in the 'Filter:' box
Also you can choose concrete country in "Params" tab (this is row-level filter). One more useful parameter is "Case Type" which allows you to switch "Cases" measure between Confirmed/Deaths/Active/Recovered (this switch because of undelying CSV dataset specifics where each row is only for one "Case Type").