The Classic task board easily fits twice as many cards.

And with the extra spacing the Rapid Board is still a lot harder to distinguish cards. The exploded UI offers little benefit.

Different teams/boards will likely desire a different degree of compactness.

Suggestions for a more compact UI:

• customisable font, the rapid board's font is unnecessarily larger than classic boards and there seems no way to change this,
• customisable card height, for example specified in number of text lines, required height would often be configured proportional to number of columns,
• remove days in progress dots, not wanted and waste of screen for some teams
• configure issue links to go to normal jira issue page, completely disabling the greenhopper issue details view,
• configure individual columns to hide sub-tasks, for example sub-tasks in the "To Do" column may need not be visible and therefore save a lot of screen UI.