Task Icon
The only area I would say improvement could be made would be eye-candy.
A couple examples:
* Perhaps introduce the idea of task icons (e.g. phone for a call). I now the small icon is already there, but it's in the background.
* Certain elements of the UI need tidying up. For example, the header font for date ranges (e.g. "Overdue"). Right now, it's too large.
All in all though, an excellent app.