While it is still in it's early stages of development, Gregg us dropping the price in recognition of potential issues (and, I suspect, to allow the user base to grow as quickly as possible).
For an introductory time, TaskTask for WP7 will be offered at a reduced price! The reduced price is my way of saying thank you to early adopters of TaskTask for WP7, since like any V1 software product there may be a few issues uncovered as the application scales out to more Exchange environments and devices than I have access to test again.
Let us know how you get on with it!