I have only swapped one of my machines to Firefox 3 because I rely on the net tab of Firebug for quite a bit of my work, and I've noticed problems with it in Firefox 3: downloads of files that were included on the page weren't showing up. It only seemed to happen when frames were involved, but as I do quite a bit of work with frames, that's a big deal for me. So I've been waiting patiently for the Firebug team to fix it, while I do my testing on my Firefox 2 machine.
Only now Rick Strahl says it looks like Firefox 3 ignores file caching rules, which totally explains why I'm missing the files from the net tab.
I'm pretty much speechless. We slam Microsoft on security and for ignoring standards, but when Firefox blocks any site that uses a self-signed or expired SSL cert, while their security team leaves gaping wide security holes in the quest for a better user experience, let alone when they go ahead and break one of the crucial underlying features of HTTP, we just sit back and say "oh, but it's open source, it's Mozilla - they know what they're doing, we can trust them." Why?
Ironic they've gone and broken one of my only two reasons for sticking with Firefox. How's Opera looking these days?