Is there a cross-platform solution for storing user credentials in the OSX keychain or Windows equivalent registry? Back in 2010 Jules said "It's the kind of thing I'd write if I ever needed it myself" (link) and it seems the new Projucer features a "remember me" toggle when logging in.
So is there a class I'm missing in the API, or will this not get into the public source code?
Well, in things like the projucer we just use cross-platform stuff like the PropertiesFile, and don't store passwords so it doesn't need to be encrypted. It'd be a nice feature to add, but not a high priority for us right now.
Can I plus one this. It’d be really useful, and it’s a tricky area admittedly with not only a different API per platform but several versions of best practice depending on which version of WIndows you are targeting… 
Then there’s some fun stuff about trying to keep passwords out of memory for too long if you’re feeling fancy