Downloaded Firefox 4 this evening. First impressions:

• Wicked fast – almost Chrome fast
• Tabs on Top – doesn’t work for me. I’ll try for a while and see if it’s just me.
• Setup didn’t get upgrades of my extensions, but another click (check for updates) did. Just a little clunky, un-Firefoxy…
• No bugs, lost files/bookmarks and so on.
• Status bar (at bottom) gone. This is an issue – can get it back, but does not behave as before (4.x). Hmm… Bad (to me)
• Normal status stuff – what the link is etc. – is now NOT part of the status bar, instead, a “toaster” on the bottom left. Hmmm….
• Last two comments seem to be Chrome issues (influenced in Firefiox). Maximize web pages; minimize the frame area (valid). So suppress (as default) the status bar. Interesting, but what does this do to add-ons, such as Firebug and Fox Weather(?) – They are currently in the status bar; how will they change/or not?

Again, first impressions.

I’ll have to see how it works with memory (Firefox 3.x could get piggy with memory…). Looking VERY good right now, but whatever.

Again, first impressions.

Update 3/24: If anything, 4.x is worse than 3.x with memory – CPU and RAM sucked up. Could be – in part – the new Flash I’ve installed, but it is still ugly.

Update 3/24 #2: Post-Flash install seems to have settled down things a bit. But need more days to draw true conclusions..