I can not recommend Nozbe at the Moment - They have to do some work under the hood to make it professional - The backup-fuctionality is a real mess compared to toodledo. In Nozbe you get a text-File including not all information you have in your account - I once messed up my account and felt on the safe side because I had a backup but it took me hours to be there where I was when I made the backup.
In Toodledo you get an XML-File really including everything form your tasks - I once made a failure in configuring a third-party-app syncing with toodledo and lost a lot - I loaded my last backup and everything was back .
Nozbe would be a wonderful tool but I do not see much progress regarding some important functionlity - and this backup-topic has been around in the forums for a long time.
For that the Price-Tag is too high
This is really invaluable information. Thanks much for pointing these issues out - that saves me a lot of time!