Hey EnergyRay,
JGLFW is a proof-of-concept implementation of GLFW and basically a huge unit-test for the bindings generator. It is not meant to replace the direct GLFW bindings. I haven't made any serious effort to make it more Java/OO friendly, it's actually an almost line-by-line port of the GLFW internal C implementation. Which is what I was trying to prove; that it's possible to write such low-level code in pure Java, simply by using the underlying OS-specific APIs.
JGLFW is both incomplete (no OSX implementation) and hasn't been updated with the latest GLFW features. At the time it was written I was considering putting more effort and having it around as an alternative back-end, but eventually decided it wasn't worth it. The point still stands though that if an LWJGL user requires direct OS-specific access and custom features, they should be able to implement their own back-end.
Other than that, the only benefit of JGLFW is custom context management. In the official GLFW build windows and contexts are coupled; you cannot configure the OpenGL context in a way that's not exposed by the GLFW API. This isn't too bad and good enough for most use-cases, but misses some important functionality last time I checked, especially vendor and OS specific extensions. I've managed to create custom GLFW builds that workaround this problem (context provided by LWJGL, window management by GLFW), but it's a bit of a pain to support properly. I'd rather make an effort to get whatever's missing into the official GLFW.
For now, my recommendation is to stick with the GLFW bindings and ignore JGLFW.