Do you have many files/images in your media folder? When you hit the "files" button it takes a long time to load as it loads all the files/images in the folder. What if you have a few hundreds of files...
This plugin adds a Quick Upload button, when you create/edit a post click the button to open a pop-up window.
By default it uploads files in blog's media folder (if you create or edit post in Blog B all files get uploaded to /media/blogs/b or whatever is set as default media dir for this blog ). You can also enable a directories select tree in plugin settings and choose a directory before uploading files.