Dashboards — What the chart tiles can do
Bar and line tiles use the same chart engine as the report page: a proper axis with round numbers, every series plotted rather than just the first, a tooltip that reads all of them at the point you're hovering, and marks you can reach with the keyboard.
Tiles adapt the data to the space they're given rather than scrolling — fewer ticks, thinner bars, labels thinned before they'd overlap — so a chart stays readable in a small tile. Resize the tile and it redraws for the new shape.
Clicking a bar or a point drills through to the records behind it, exactly as it does on a report. A tile you've just configured and not yet saved drills too.
A tile that measures a rollup, lookup, formula or auto number resolves it properly — totalling a rollup is one of the most obvious things to want on a dashboard. If a measure can't read anything, the tile says so and points at the setting rather than drawing a flat line at zero. Blank cells are skipped rather than counted as zero, so an average isn't dragged down by records that simply have no value.