The _changes comet feed as a replacement for the update notifications is a great step forward, but I'm currently missing these features:
1. The feeds are now per database, rather than per server, which is nice in some use cases, but in others it's preferable to have a server wide feed (In the case of many thousands of databases on a server, and a single process reacting to updates, by putting messages on a message queue for instance). Ideally I'd like to have both server wide and per database _changes feeds available.
2. I'd like to have a configurable _changes feed that let's me declare what data will be output in the update rows in the feed, in a similar way to writing views.
3. I'd like to (optionally) have information on whether a particular update was a document creation, update or deletion, so clients would be able to react to those differently without needing to query into the database to find out what happened.