For now it is disabled by default to not disturb unsuspicious users. You can enable it in Settings -> Display -> Emulators -> Borders when using the original 4:3 mode. Also there are some settings that we exposed to let the users make the border more prominent or more subtle as they wish.
Note that this first release covers only the systems emulated by RetroArch, we will continue working in the other emulators the next days.
We also changed the default settings of the PSP emulator to make it run smoother by default in devices that has enough power for it (Nvidia Shield).
Last but not least, in this version we added more details when reporting errors on NAS devices, hopefully it will help us diagnose the user that still have problems with it.
However since the update some of the Video Shaders now no longer work when using this setting (see pic) and just show a black screen with sound or flip the image upside down. This is for original and strech to fit screen. The Hqx-hqx2 one does it and is listed twice in the list.