Features I was looking for:
- free
- support for recurring tasks by due date and completion date
- notes for tasks (ie separate notes field / additional to the task title/name)
- reminders independent of due date
- sync to cloud / PC / other devices (I currently sync between Google Tasks and Astrid on two devices)
- automatic backup, restore, and export (see next point)
- data compatibility with other similar apps (ie in case need to transition again)
- (optional) priority levels
- http://www.androidauthority.com/astrid-alternatives-201278/
- https://sites.google.com/a/umich.edu/going-google/top-faqs/task-managers
- http://alternativeto.net/software/astrid/?platform=android
- https://docs.google.com/spreadsheet/ccc?key=0At4J5a3i2zW8dDhUeGFJbFFORFhNQU5vRW8xZmRxX2c#gid=0
- Gtasks
- syncs with Google Tasks
- does not support recurring tasks in free version
- the above limitation pretty much killed it for me, so I uninstalled Gtasks after installing TickTick and importing from Gtasks to TickTick
- TickTick
- based on/evolved from Gtasks? No longer tied to Google Tasks.
- can import from Gtasks, but sync is with own cloud
- reminder/alarm is tied to due date
- cannot set recurrence by completion date (only due date)
- cannot set recurrence by more than 2.5 years (30 months) - I currently have one task that I want to recur every 5 years
- overview screen/list only displays 1/1st line of task title
- the combination of the above few limitations meant my search was not yet over
- Wunderlist
- can only import from Astrid.com
- I wasn't using Astrid.com, but could do a one off sync from Android to Astrid.com, then use astrid.wunderlist.com to do the import into Wunderlist - this produced duplicates of everything, but otherwise worked fine
- sync is with own cloud
- can maintain multiple lists
- can set reminder separate from due date
- email notification setting done via website seems to apply for normal reminders as well as what the website suggests (other things)
- cannot set recurrence by completion date (only due date)
- overview screen/list only displays 1/1st line of task title… (but at least this is denoted by "…" cf no indication of more text in TickTick)
- selected sort order (eg by due date) does not autorefresh after changing a task's due date (or it might take a minute or more, which is a bit off-putting)
- reminder notification cannot be persistent (as Astrid's could be)
I also briefly considered how I might extend my use of Evernote, or play around more with Google Keep, but they're notetaking apps and not to do apps. I also subsequently found out I could keep using Astrid offline / syncing only to Google Tasks (which was my syncing regime in any case), but figured I didn't want to be 'stuck' with old and frozen software.
So, Wunderlist it is... but I am going to miss Astrid.