I've been using ToodleDo with Appigo's Tasks for quite a while and I've just migrated all my tasks to Google Tasks. I was finding ToodleDo/Tasks a bit heavyweight for my requirements and I love having my task list within my GMail window ready to go.
Found GeeTasks this morning. Installed the free version, then almost immediately bought the paid version. Very nice job!
The icon could do with being a little less obtrusive - mainly because when the notification red circle is up, the amount of red on the GeeTasks icon makes it a little difficult to spot. Also because it is just too bright and stands out too much on my home screen ;-)
A feature that Appigo Tasks has - when a task is checked off and moves itself to the bottom of the list (love that BTW) - it hangs around in a checked state for half a second or so. A nice visual confirmation that the task has been checked off.
John