This is one of the reasons why I dumped my iPad. I loved using it for most of the time, but when it came to file management - forget it. I didn't have a desktop computer to manage files on my external hard drive so I plugged it into a router and accessed it through the network. It worked for managing a limited number of small files, but if you had to do a backup or manage large amounts of files, or do another backup of the external hard drive, forget it. The iPad just wasn't up to the task. File management on the iPad works if you've bought all your music, movies and manage your photos with Apple and pay for the extra storage, or if all your files are in cloud storage, but I had an extensive music and movie library burned from CDs and DVDs that I had to backup. Also, managing photos without iCloud on the iPad is a nightmare. Duplicates galore. Not everyone wants to store their photos on cloud storage.
The iPad was clearly meant to be used with cloud storage and people should be aware of this limitation before buying. In the end, I got frustrated with the workflow and am tired of giving my money to Apple to pay for storage, iTunes match, etc. I want total control of what files I can manage and where I store them.
I think this new File App will disappoint a lot of people. It's still sandboxed and people expecting to hook up an external USB stick or hard drive, or drag and drop files by hooking it up to a computer, will be let down. People wanting to do this will need to turn to Android or Windows. If Apple opens it up a bit and extends the functionality of the File App, then I may be tempted to get another iPad, but for now I've switch to Windows to do this work.