The new colour scheme and subtly tweaked interface. I could be imagining it, but responsiveness seemed better too, at least with the fairly short 'pages' used by default by each store section. There's also, on the touch-enabled S60 5th Edition version at least, no attempt now to try and detect 'swipes' on the top category bar - simple taps on panels or on the arrows are used instead, also improving responsiveness overall, I suspect.
The new Help 'FAQ' page, plus the new loading screen - minimalist in the extreme! No Ovi branding at all though - to be essential in the coming days when the Nokia Store has to be just that - Nokia, spanning multiple smartphone and feature phone platforms.