Overall: It's an improved look. I knew they were in trouble when a large number of third party apps looked better than Apple's stock apps. The shine/skeumorphism/drop shadow overload had gotten out of hand.
That said, the typography is rough. Helvetica is already less than ideal for viewing on a screen (especially at small sizes), but making it light reduces legibility even more. Thankfully there is the "increase text legibility" option in Settings.
Lastly, I'm not sold on the button-less text buttons. I think that buttons work fine without a border when they are iconographic. It's a little tricker when they are text only. Especially when the text is stacked.