ToDo list, with SPECIFIC repeat option I'm looking for a simple to-do list, that preferably is cloud-synced. I'd like something with a relatively light-weight, simple interface, similar to Any.Do or #fetchnotes. I was using CheckMark Pro, but it is really WAY overkill for what I want. 

My biggest criteria is that I want to be able to set a task to repeat, some interval from the date it is completed. Most of them let you repeat every 6 months or 2 weeks or whatever, from the due date. But take this example: 

Task with due date of 5/30. 
Task set to repeat every 6 months from completion.
I complete the task, marking it done, on 5/13. 
The next occurrence should now repeat 6 months from 5/13 (the completion date), not from 5/30 (the original due date).

And of course whatever reminder is set (2 weeks for example) should be relative to the new due date, 5/13 in the example above.

Most of the one's I've looked at either are not cloud-synced. And I've not found any others than CheckMark Pro that allow the next occurrence to repeat based on COMPLETION date rather than DUE date.
Astrid has support for scheduled reminders based on completion date.

Cloud support is also present - tasks sync with astrid.com



Also Remember The Milk allows a user to schedule due dates depending on the completion of a task - one needs to enter "after x days" instead of "every x days". Android and iOS apps available.