There's many other problems with FF3 on OS X then the basic GUI.
Because Mozilla chose to use XUL for as much as possible instead of taking it from Cocoa or Carbon. Nor do they share the same keyboard shortcuts (when typing, to move to the front/end of a line in Safari, then in Firefox for example).
By using Carbon, FF doesn't take any of the Accessibility features most other OS X applications have (like Voiceover). Not to mention the devs will have to rewrite these bits for 64bit support.
Grubar did a write up of FF3 vs Safari 3 awhile ago: http://daringfireball.net/2008/04/firefox_3_safari_3 - other then the Background/Foreground bit at the very beginning, it's still accurate. Though there's still Background/Foreground issues if you look closely (the tab bar when there are no tabs looks like a foreground window no matter where its located for instance).
It is true, and I think it is short sited of the Mozilla devs, sure porting to use the standard toolkits would be a bitch, but basically they just re did all the work to copy the "Look" of the different kits. That doesn't scale well, instead of a project to make it native on a couple systems once that would take a lot of time NOW, they have a new system which will require getting upgraded with all the new OS version.
"Not to mention the devs will have to rewrite these bits for 64bit support."
Huh? Why? "64bit" doesn't change the APIs, at most it should take a recompile to build against the x86-64 version of the libraries. And thanks to Universal (fat Mach-O) binaries one single executable can contain ppc, x86, and x86-64 versions bundled right into it.
If the rest of my OS is going 64bit, why shouldn't my browser? Besides, I would imagine (unfortunately I'm not as well versed in this area as I would like) that there would be a performance gain from using a native 64bit browser on a 64bit OS instead of a 32bit browser on a 64bit OS.
True, some plugins for browser (I'm looking at you, Flash) aren't 64bit - yet - but that could be vendors dragging their feet because there's not enough of a demand. Or something else; I'm not privy to what goes on in the upper levels of Adobe. Or any other major company for that matter, but thats not the point of this post.
Browser developers have had to jump through all sorts of hoops to get 32-bit plugins (aargh, Flash!) working in 64-bit browsers, (e.g. on x86_64 Linux distros) but it's presumably even harder to do the opposite, use 64-bit plugins from a 32-bit browser. My x86_64 Linux distro has 64-bit Java, for example, which won't work with 32-bit browsers.
Aside from that, it won't be long until 64-bit operating systems take over even on the desktop, even in Microsoft-land, and the less 32-bit cruft that is dragged around, the better.
Regarding Carbon and Accessibility, VoiceOver, etc.:
Every standard view on Mac OS X receives accessibility and VoiceOver support, whether it comes from Carbon or Cocoa. So Carbon isn't the reason this breaks in Firefox.
Because Mozilla chose to use XUL for as much as possible instead of taking it from Cocoa or Carbon. Nor do they share the same keyboard shortcuts (when typing, to move to the front/end of a line in Safari, then in Firefox for example).
By using Carbon, FF doesn't take any of the Accessibility features most other OS X applications have (like Voiceover). Not to mention the devs will have to rewrite these bits for 64bit support.
Grubar did a write up of FF3 vs Safari 3 awhile ago: http://daringfireball.net/2008/04/firefox_3_safari_3 - other then the Background/Foreground bit at the very beginning, it's still accurate. Though there's still Background/Foreground issues if you look closely (the tab bar when there are no tabs looks like a foreground window no matter where its located for instance).