Just got the beta...Colour me impressed. The GPU acceleration definitely shaves clock cycles off the processor, opening a large amount of tabs simultaneously is lightning quick, there is no UI lock while web pages are rendering so you can scroll around even as elements are not yet loaded, making it feel faster (hey google, DO THIS), and the new interface is nice.
Not so good are the dubious decision to put tabs on the same horizontal space as the address bar, squishing it. And of course a big one is lack of the massive extensions gallery Chrome and FF already have.
Something else to consider is GPU acceleration and battery life. Watching GPU-Z tells me my graphics card jumps up to 680MHz from 200 wheneever I scroll. I hope someone (cough TOMSHARDWARE cough) does some battery life tests of all the latest browsers soon, I wonder if offloading to the GPU will increase or decrease battery life.