Ask HN: Do you use ETags for performance?

I'm in the process of improving the performance of my app. Some stuff can be browser-cached, some stuff can be public-cached, but the data doesn't change much, and when it does I want the user to get the latest. At some point I'll probably have to setup programmatic cache-busting with a CDN.

People don't talk about ETags nearly as much, and I know it's not the same performance gain as a cache, but are people using them in the wild? My instinct is the performance gain from not downloading vs calculating the hash should be a clear win (if a small one).