It would be nice to be able to have settings apply app-wide and not be user-specific. It's workaroundable with backing up settings through one account and restoring from the second one but a native solution would be nice to have.
Hidden posts only seem to apply to the feed and not carry over when viewing specific communities.
I've been using sync for a while and Lj added the "comming soon" message to everything he was still working on during the closed beta. I guess that's one of the very few functionalities which aren't added just yet.