The app we're talking about is Kingsoft Office for Android.
This app has pretty much everything you'd expect to find in Quickoffice Pro. It's compatible with MS Office files and allows you to create, edit, view, and save them. The built-in file manager is another nice feature, which allows you to search for files on your Fire if you're not sure where they are. The interface has somewhat fewer features than Quickoffice, but that shouldn't be a problem unless you're doing something completely out of the ordinary. Let's take a look:
Unless we find anything fishy about it, it's very possible that our go-to office app for the Kindle Fire will be Kingsoft Office for Android! At the very least, save yourself the $15 and give this a try first to see if it works for you.