But Google Reader has just changed, and some syncing RSS readers will lose some features, and I take that as a reminder that it could change in a way that breaks syncing, and Google would not have broken any official APIs.
I’m not an RSS reader developer any more. But if I were, I’d start looking for an alternative syncing system right now.
I wish that NetNewsWire hadn’t switched to using Google Reader for syncing in the first place. The Google syncing of the read and flagged status was unreliable for me. Plus, it seemed to delay receiving new items (compared with downloading the feeds directly), and I would sometimes completely lose unread content if the author later deleted or revised the item. Plus, I’d prefer to put this data on another server, rather than entrusting it to Google.
Update (2011-10-25): Of course, that’s not as easy as it sounds.