The new interface is really much faster than the old one, but the frames behind games (also the individual coloring on them - I tried switching this option off, but didn't work) make it a little too much. The spacing between systems on the left panel could also be smaller. With the old interface, I could see all of my systems in the list. Now I have to scroll to see half of them (even after reducing font size to 9). The same goes for the right panel.
I wish there was a way to at least "skin" (is there - or will there be?) the new one so it would look more like the old one in this sense, without the frames behind each game and with smaller spacing. Then we would have the best of both worlds.
But, regarding speed, there's absolutely no doubt the new one is way better.