Here's the full list of new features in the 5.0 beta, according to Kevin Barry:
New Pixel Launcher style searchbar
New search view, with tabs for Frequent, Recent ad New/Updated apps
New "Timeout" screen lock method
New double-tap-swipe gestures
Integrated searchbar into drawer (card and immersive)
Option for dock backgrounds to draw under navbar
Nougat fixes and optimizations
Improve interactions with KLWP
For my money the coolest new feature is in app searching, which is now split into three different tabs for more quickly parsing through the apps on your phone without manually setting up drawer folders. The developer recommends a few settings if you want to emulate the Pixel launcher completely: enable swipe to open the dock, disable the card background and set the background color to white, set page indicators to lines, and set the dock background as a white transparent rectangle behind the navigation bar.
All that said, none of the new additions really affect the core functionality of the already-solid launcher (with the possible exception of Nougat users), so don't be in too much of a hurry to try the latest version of you're already happy with Nova.