Agree about adding a feed, will check up on where that stands. Honestly, it hasn't come up often (that I'm aware of) since the first days, so it may simply have slipped lower on the priority list, but I'll ping the team for an update. The engineering complexity was that we'd want to serve feeds out of the same servers as the read/write API itself, but the full API requires dev keys and auth, so we had a feature under development to allow certain calls to have different auth (or in this case, no-auth) models. Certainly not that feeds are a bad idea at all.
Also, what we learned from Buzz (which had feeds as the primary
API surface) was that the feeds work best as a serialization mechanism for content intended for feed readers, but when you just take standard Activity Streams output (like we had for Buzz) it doesn't render that great in a typical reader. So we're working on new templates designed explicitly for that use-case, rather than conflating the read/write API with the feed like we did before.
And for what it's worth, the new Google+ API is Activity Feeds and Poco and OAuth2 and other community-developed protocols, all serialized in JSON—so fortunately not yet another snowflake. We saw the JSON trend coming for a while, so +Will Norris
and others here spent a considerable amount of time prepping the AS community for a JSON-based version.
Hope this helps!