I built a simple Atom service for Gerrit, available at:
http://schmerrit.wmflabs.org/gerrit/changes/<repository>.atom
For example, here's the feed for mediawiki/core:
http://schmerrit.wmflabs.org/gerrit/changes/mediawiki/core.atom
Is this useful for people? It scratches a personal itch I've had, but I'll only put in the trouble to make it robust and reliable if someone other than me finds it useful -- so please let me know if you do.
Right now there's no caching at all -- all the content is generated dynamically by making calls against Gerrit's API. So go easy on it.
Ori