I've recently installed this browser and I've noticed a few differences from FF2.
I'll have to use it longer to give a more insightful review of this product. For now I'll give it a 3 (out of 5) because half of the add-ons (eg, Firebug which I find very useful) I've installed with FF2 are not compatible with this version.
I'm actually giving this a try because of one add-on that works only with this version and that is the Internet Explorer (IE) tab. It lets you use IE using Firefox. Confusing eh? lol. This way I get to open two accounts (say, Multiply) without opening IE. And did I forget to mention that it loads a lot faster than using the actual IE? Ok, this is starting to sound like a review for the add-on rather than the browser. lol
I'll make updates regarding the browser as replies to this post. Meanwhile, you may wanna try it keeping in mind that this is Beta version.