I use 85% Firefox and I only see issues on experimental stuff. I'm curious, where do you have these issues?

Firefox is a pain to support. Its box model is slightly different than other browser, like shadows take up space and an outline is rendered around the shadow instead of aroubd the border. There are other minor things especially on the drag&drop events (in same window, not from outside) but I can't recall the specific.

Yes. The latest version of Firefox has cache issues. The same in Chrome was working perfectly after a single refresh. Sad. I love Firefox.

Chrome does not obey cache headers on refresh, I think they assume something is wrong if you are hitting the refresh button and fetch all files from the server.

I can't really blame firefox for obeying the headers that the server sent them.

This problem hit me very hard, chrome ignores most headers if a server sends a 304 response for a resource.

For a site I was working on, we issued a change to our CSP headers only to attempt to fix a CSP issue that made it to production, and chrome would not accept the new CSP changes since the HTML body and scripts were unchanged.

Had to include the hash of our headers as an HTML comment to allow this dynamic change to be picked up by chrome.