It’s in RC now, so pretty much baked.
Panorama. It’s an interesting feature/solution to handle many tabs. I feel that it may not catch on with casual users. Maybe with some power users. It feels clunky to me. It has potential, but it needs improvement and a more visible integration.
Multi-process. Firefox doesn’t have a full multi-process tab design yet, but it does have sandboxing of several, if not all, plugins. I don’t seem to have plugin crashes much in Chrome or Firefox, but it’s definitely a nice feature. Mostly, though, I like being able to kill a single tab in Chrome. In Firefox, if it’s not a plugin crashing, the whole app hangs. Super annoying. I have had a few whole app hangs with Chrome, but not as much as Firefox, I think. Also, Firefox occasionally has really random crashes, while Chrome tends to be pretty solid.
New add-ons page. Stuff in a tab, kind of like Chrome. I like it, though it’s inconsistent. The rest of the settings are still in a window. That won’t bother most people, I think, but it’s a little strange.
Speed. Firefox keeps improving, though it seems destined to always lag behind WebKit. I’ve heard that Firefox 4 start up times and general operation speed are also pretty good, maybe even comparable to Chrome. Even Chrome seems to take a little while to start up on my system, though, so I’m not really one to judge speed.
Tabs on top. Nice change. As I saw someone saying, it makes tabs easier to understand since they look more like physical tabs in a file folder. Unlike Chrome, the original window decoration is kept, although the tabs and Firefox button can cover most of it. I’ve gotten used to it, but Chrome’s use of non-standard window decoration still bugs me.
New theme. On Windows XP, simple, unobtrusive, and neutral with subtle highlight effects. I approve, because the XP theme in Firefox 3 was ugly. I’m not sure yet about the Firefox button, but I have a feeling it’s easier to navigate than Chrome’s menu. I also like the classic menus disappearing—apps look so much cleaner without a bunch of them.
Miscellaneous. Now has pinned tabs like Chrome. I prefer the way Chrome’s behave, though. Now has a syncing service like Chrome. If you use more than one OS or computer, it’s an easy way to keep things synced up, which is more important than you might think when your browser is about your most used app.
I was a Firefox user for a long time. Chrome made a surprise appearance and I liked it, but didn’t feel comfortable enough switching each time I gave it a shot. At some point, the state of Chrome, especially of add-ons, clicked and I switched over. I try Firefox now and then but can’t really switch back to it full time. I’ve become very comfortable with the way Chrome does things. I still hold out on Firefox for web development, though. Chrome has a pretty good dev tool, but I prefer Firebug.