I just installed Firefox 2.0 Beta 2 on my MacBook Pro a few seconds ago and I'll post my observations here as they happen:
Smooth scrolling with trackpad gestures (two fingers) is actually smooth. It now behaves like it does in Safari and Camino!
Typing is more responsive!
Actually, the whole UI seems more responsive.
Fast-back is basically instant now, like Opera.
Suggestion boxes, the url entry line, and other tooltip-ish things have a fade out effect.
You can open all recently closed tabs at the same time using the history menu.
The Extensions and Themes menus have been combined into an Add-ons menu.
A few of my old extensions, such as DownThemAll and Adblock still work.
The stationary tab-closing button that used to reside on the far right of the tab bar is gone. Oh well, I still have cmd-W.
Underline-as-you-type spell checking!
It does sessions! And, it's smart about crashes, offering the choice of a clean start or a session restore during recovery.
It has auto-suggest in the built-in Google search box.
