UI Changes when installing addonsOn Kodi 17.6, to install a new addons required you to go to System first (to add in the repo) then go back to the homescreen to install from zip file and the addon). In Kodi 18, the system screen now has a section for both File manager & Addons.
Gaming - Kodi 18 brings gaming to the forefront. You get access to a large library of emulators with associated control support. No need to install manual repos / emulators.
Dependency changes - On Kodi 17.6, you could try and install an Add-on but if it failed, it was not easy to see exactly why it failed. Was there a missing dependency? What didn't install etc. In Kodi 18, each addon as a dedicated section for dependencies so you can see exactly what dependencies the add-on needs and what are already installed.
DRM Support - You can now install the official Netflix (or any DRM supported add-on) and watch it directly in Kodi 18 in full HD.
PVR Client updates
Overall speed and UI tweaks.
You can see a video of the new features, including retro gameplay here