Of the many to-do apps available in the App Stores, one of the perennial favorites is Things from Cultured Code (US$9.99 for iPhone/iPod touch, $19.99 for iPad, $49.99 for Mac). While the cross-platform app has been lauded for its beautiful user interface and ease of use, there have been continuing complaints from users who want to be able to sync their to-do tasks between devices. Other apps, like Wunderlist (free) and OmniFocus, have had cloud syncing for a while, and today Cultured Code has finally taken the wraps off of an implementation of cloud sync.
The beta is open only to registered beta users, so most Things users won't be able to get their hands on the service yet. The beta is meant to test the ability of the service to handle automatic cloud syncing. Rather than requiring the user to manually initiate a sync by tapping a button, Things will sync whenever you launch the app, switch from another app, or wake a device from a sleep state.
Cultured Code notes that its sync solution features encrypted transmission of data, so your top secret to-do items can't be intercepted in the clear. We don't know for sure when the Cloud Sync service will actually become available to all users, and given the slow rate of development from Cultured Code in the past, it's almost a certainty that user complaints will continue for some time.