In the first 24 hours since its release yesterday, Firefox 3.5 has been downloaded more than 5 million times . (It took only a few hours to pass a million ). That is certainly respectable, but doesn’t quite measure up to the mania that Firefox 3.0 set off last summer, when it achieved a “world record” 8.3 million downloads in a single day. Maybe we’ll have to wait for Firefox 4.0 to beat that record. But Firefox 3.5 might still beat the 11 million downloads Safari 4 got over its first three days of availability. Who’s.among.us has some live usage stats from about 800,000 Internet surfers it is tracking. According to its data, it estimates that Firefox 3.5 already has gained about a 2.4 percent browser market share. Overall, it puts all versions of Firefox at 29 percent. That suggests close to 10 percent of Firefox users have already upgraded. It also puts Safari’s market share at only 2.5 percent, which seems low. (

Other stats put it closer to 8 percent). Looking at our own Google Analytics for TechCrunch, 28 percent of Firefox visitors are already on 3.5, but our readers are big Firefox fans—nearly half of all visitors use some version of Firefox, which is a much higher percentage than for most sites. I’ve been playing around with the 3.5 release candidate for about a week. It is much zippier than 3.0, and I’m already addicted to the plus-sign feature on the tab bar which makes it easier to add tabs. And I love where it’s going with open video standards . It is also a bit crashy when I have too many tabs open, but that’s getting better. Some add-ons don’t yet work, but nothing crucial. Overall, it’s a much better product. Crunch Network : CrunchGear drool over the sexiest new gadgets and hardware.

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Firefox 3.5 Hits Five Million Downloads in 24 Hours. Respectable, But Not A Record.