Matt has a blog post asking for customer feedback on the removal of OnSyncSave and OnSyncDelete from the next version of Exchange. Go over there to read it, or check out this snippet:
I am working with the product team to discuss any scenarios where EWS notifications and Transport Agents might not be sufficient to replace synchronous store event processing in a custom solution. The Exchange development team and my Exchange support team are aware of the potential challenges arising from changing the development interfaces available. Between Exchange Web Services notifications and Transport Agents we feel that we can fill a lot of the gaps left by removing synchronous store event processing but we want to hear from you. Are there scenarios that you currently require synchronous event processing for right now? Please email me or leave a comment describing your scenario. Getting your feedback will help us prepare documentation, workarounds, or solutions that can mitigate the challenges presented by this change.
So if this is a concern to you, go over there and give him your feedback.