There's a reason why it can be argued that tabs are a bad idea. Tabs overlap the functionality of your choice of window manager and panel, and don't behave as your choice of window manager and panel. It can be argued that they're reinventing your desktop environment and have a long way to evolve into something as good as the existing desktop environments, for no minimally relevant advantage at all.
I've wanted to get rid of tabs long ago; it took me a lot of time to switch over to Chrome/Chromium and it was because of them. I ended up falling for these tabs, but not because they convinced me that they were any good; it's just that Firefox is so horrendously, abhorrently slow (especially at rendering text) in GNU/Linux that it drove me sick.
We're living though times for UNIX. Every good thing UNIX ever had and abstracted is getting killed. The command line (we need a big GUI project for every retarded thing you'd do in a line of shell), the window manager (tabs, and the GNOME guys want to kill it too for some aberrantly retarded reason), the X window system (they want to turn it into a Terminal Server type hack), and even the freaking filesystem (they seem to think people won't understand directories and will be settled with just "My Music", "My Porn" and whatever cheesy stupid thing they come up with).
I'd equip cars with near-field communication... the only message in the protocol would be "Fuck you!"
The biggest bug: OpenGL for GNU/Linux is still under work.
If only Mozilla dedicated to the GNU/Linux version a tenth of the effort it dedicates to the Windows version, it wouldn't be easily the slowest browser in the platform and lack such essential 4.0 features. As it stands, it has nothing to do with Google Chrome.
If all Mozilla cares for is fighting MSIE, they should drop the Linux port rather than posting an unfinished, unoptimized product.