Recs.
Updated
SpecsUpdate
Pros
Pro Flexible recurring tasks
Recurring tasks are simple to set, and can be created according to custom rules.
Pro Has a calendar view
Pro version of the software allows tasks to be laid out in an easy to overview calendar view.
Pro Keyboard shortcuts
TickTick supports keyboard shortcuts that makes it easier to work with.
Cons
Con No native integrations with IFTTT or Zapier
The app doesn't feature native integration with these services, but you can use this functionality by fiddling with the custom email address that is provided by TickTick.
Con Intelligent date and time entries don't work everywhere
In some apps, you can type "call Ben tomorrow at noon" and the date and time fields will be automatically populated with "tomorrow" and "noon". TickTick has recently implemented this feature, but it doesn't work flawlessly via the webapp or via a widget. The functionality does work good within the Android app, however.
Con Free version is limited
TickTick's free version is limited to 19 task lists, 1 attachment per day, and 1 collaborator.
Con No search of non-latin languages in web
The web version has no ability to search non-latin languages (e.g. Russian, Greek).