I've been using Firefox 3 Beta 2 for weeks now, and it's absolutely amazing. There's not much else to say other than that. Just a few quick points, and then I have a gripe.
The Good
Memory consumption is so amazingly low compared to Firefox 2. I actually don't find myself constantly killing my browser these days.
GNOME/GTK+ integration is finally up to par I think. Browser shell widgets look more native, web controls look native. Fantastic icon theme integration. Firefox finally feels like part of my desktop now. Kudos to all the great GNOME love. It's about time!
The new location bar drop down is awesome.
There are subtle attempts of humor.
It's been rock solid, more-so than Firefox 2 ever has been, barring the typical Adobe Flash freezes.
We have packages with proper distro-integration patches for openSUSE 10.3 (1click Install and yes, it will replace your Firefox 2. I live on the edge!)
The Gripe
I hate the new full page zoom! So many people rant and rave about how awesome this feature is. It's horrible. It breaks usability and accessibility of web pages. When reading a page in a properly designed web site (proper semantic markup and good CSS) in Firefox 2, text would re-flow properly when I zoomed. This allowed me to read a page with increased zoom without breaking the layout of the page, but also not causing it to scroll horizontally. In Firefox 3, everything zooms in, often causing me to have to scroll horizontally to read the page in question. Utterly bad. The closest thing I've been able to do is setmousewheel.withcontrolkey.action to 3, causing text zoom to happen when I hold control and use the scroll wheel. The problem with this is that it's hard to know how many levels you've zoomed (I have an insane scroll wheel with ball bearings... it's very fast and sensitive) and there is no reset (like CTRL+0, traditionally). Also... I just like CTRL++, and CTRL+-.
