Firefox 4 was launched on 22nd March. Just upgraded from Firefox 3 a week ago. Totally regret. That I waited 3 days after downloading the setup file before installing it.
Huge and noticeable difference from the get-go. FF3 took around 2 mins from launching to showing up as browser to finish loading all the plug-ins and add-ons (I’ve got like 20 of them). In all those 2 mins, CPU util spiked 100% with the browser not responding. From there, loading a new page will caused the browser to freeze anywhere from 30 secs to a minute.
With FF4, 30 seconds flat from launching to usable browser. That really surprised me at the first time. I’m well pleased 
Another improvement was saving bookmark. While FF3 will take around 5 seconds for the Save Bookmark pop-up to appear, in FF4 it’s almost immediately.
Although some plug-ins are not compatible with FF4, a quick hack with the rdf files fixed it. But you’ll notice it’s a quick & dirty hack when the plug-in behaves rather quirky, like transparent menu for the LeetKey addon.
One thing that didn’t change is the RAM usage. With 3 tabs open with sites that are pure texts, the RAM util still go well above 250MB when left open for an entire day (~12hrs). But it didn’t lag or jerk like FF3 does, so I’m still ok with it.
All in all, I totally heart FF4.
Posted by hsyeow 
