We collect statistics on Task statuses, and then display them in a graph. This works great (see attached figure 1).
We also calculate the difference between today's statistics and yesterday's statistics (and this week/last week, this month/last month), and display those beside figure 1. That doesn't work so well (see attached figure 2).
It would be cool if there were a graphing mode that showed positive and negative numbers nicely (see attached figure 3).
In general, more advanced graphing widgets would be fantastic.