May 28: 1.6.1 fixes a few crashes. May 30: 1.6.2 fixes some more. June 5: 1.6.3 fixes even more.

OpenGL backend now properly multithreaded, giving a good speed boost.
Various Vulkan performance improvements (like #10911) and memory allocation fixes.
GPU command interpreter performance improvements (#10658)
Various fixes for app switching and widgets (#10855) on Android
Bugfixes and some performance improvements in the ARM64 JIT compiler and IR interpreter
Shader cache enabled for Vulkan
Multiple iOS fixes, including JIT (#10465) and file browser (#10921).
Improved compatibility on Mac (#10113)
Texture replacement ID bugfix (note: some textures from 1.5.4 may become incompatible)
Adhoc multiplayer fixes (#8975)
Vulkan support on Linux/SDL (#10413)
Retroarch support
http://www.ppsspp.org/downloads.html