I guess this has been stated above already but anyways...
The old UI at least for me was perfectly fine. It might've been very hard to get into (honestly I opened the tutorials even before opening the program itself so that didn't really apply to me in full effect I guess), but once I got used to it it felt extremely clean and fast and that, in my opinion, matters most in that kind of applications. Multiple and highly customizable views, lots of shortcut-only actions... you get it. As for the new one, let's just say that I might give it a third try once I get a 1900x1200 screen. I was able to use 2.4x on resolutions as low as 1024x768 perfectly fine. And yeah, that's about it for the interface :)