One part of me doesn't like how much space is wasted by the new Mac UI trends shown in the second screenshot, mostly the left side panel. But I understand screens are different these days as well.
I assume you are referring to the inspector panel on your other left; the two main reasons it is wider are (1) that it shows HTML5 validation error text descriptions in the 3rd tab and (2) this is the same width we use in our other application Hype, so they now look like they belong together. I did have a moment of feeling that I was contributing to the "war on information density" with this change.
I'm glad that the brighter colors are more subdued now, annoying UI elements like drawers and palette windows have mostly been replaced by inspector panes, and brushed metal is long gone.