With that layout, will an end user be able to clean up resources easy enough, if they want to clean up/make space?
Search for 'lwjglcache' folder and delete it would be the easy way. Probably could even make an applet to do it for you (like adobe have a flash control panel on their site to allow clearing cookies and various settings).
"deployment.user.cachedir" returns a value on Windows, I really think that "java.io.tmpdir" is good for windows, what is the benefit of the "deployment.user.cachedir"?
There's not much difference IMO between the two locations on windows, both are equally difficult to find for the average user. Main reason to use "deployment.user.cachedir" is that its a single parameter that can be used on all platforms without getting bogged down in platform specific settings and likely more future proof. Other then that there isn't any big difference, can still be changed if you like.
I think your original idea of a hidden folder in the home directory (if not Windows) is better. Wondering If I understood the new version right?
Yup was the original idea but wasn't sure how it'd be like on Mac, after reading a few documents on the apple site, they actually recommend that application cache be stored at ~/Library/Caches/* so using the above parameter automatically puts cache files in the recommended location.