The other storage isn't a problem really. I figured it out. WP caches almost everything intot that storage so you get a blazing fast os. Try this: delete a picture with pocket file manager or some other app. Quickly come back to gallery and open that pic. It'd be there, you can zoom in into it even, it'd stay there till WP realises it is gone. You cant open it with any app, because the pic isn't there, but it had been cached already which takes up lot of space. So with music+videos. And your home screen tiles, all that is cached, and takes a huge amount of space. In return it gives you super fast speeds
But i have system files of size 2.70 gb....a friend of mine who got L525 has only 2 gb....whats wrong with dat?? Is MS adding other files to system files category??