You are now able to upload files via WiFi File Explorer by using drag-and-drop. The old upload box on the web user interface has been updated to display an area that allows you to drag-and-drop the files you want to upload, to make it quicker and more efficient to transfer files from your computer to your Android device.
So just drag the files from your computer onto the new area labelled "Drop Here" and your files will immediately upload. You can still use the "Select Files" button if you wish to navigate to your files in the more traditional way.
Aside from being a more convenient way of transferring files, another benefit of this update is that is no longer relies on Flash plugins to handle the upload; instead it uses HTML5 and JavaScript. This means that some older web browser may not support the drag-and-drop mechanism, so you should use the "Select Files" button instead... or get a better web browser! As Flash plugins become more and more obsolete, this update helps to future proof WiFi File Explorer as Flash will eventually become unsupported.
Let me know if you have any issues with the new drag-and-drop feature - it's a lot of new code, so there could be bugs I am yet to find through my own testing.
Also, there's a new tidied up and higher resolution icon, and a new font for the logo title, as you can see in the image above.