I can help with the UI part- https://zddemo.ruckuswireless.com
is a demo instance of the ZD, running 10.x. It's like a cross between the menu system of the SZ 3.5 and the content of the ZD's menus- no real significant differences in content/location.
In the release notes, the "Enhancments" section covers the new features. As for "big" updates, that's all relative. I can tell you that Spectrum Analyses isn't what I'm looking for most- the ZD1200 doubling its AP count and OFDM in the GUI is.