Listary looks very interesting. A great find. I'm going to give it a try.-DanJak
I found it on discount at
Bits du Jour.
This is a hint. 
I also bought a number of software licenses via DonationCoder discounts.
This is another hint. 
The Free Version doesn't require installation so could be used as a portable application.
It would be nice if all versions could be portable; I realise this may not be possible.
The Professional Elite Version of Buzz Folders remembers your recent files.
I'm English, and unemployed. The Professional Elite Version of Buzz Folders costs £36, which is too much, the more so if the licence is per-computer, which is how I read your EULA. If it were portable and the license allowed home computer plus portable, that would be nice.
However, it looks like I didn't explain what I meant well enough. The screenshot below is a common-or-garden File Open dialog in Adobe Reader. You'll notice that the cursor is on a file. What I wanted was a dialog box extender that would re-open the File Open dialog
with the cursor on the same file, or, optionally, on the next file down (or up) in the list. I admit I got fixated on this because of a particular task I used to have to do at work. Now I'm work-free the task has gone away, but the idea is still one I'd like considered (or definitively shot down as completely silly).
list of files displayed below the folder buttons and the last file you opened will be at the top of the list. Opening that file is as simple as pressing the "GO" button.
Perhaps you could implement what I mean by allowing Up Arrow or Down Arrow to scroll through the list from that file, though it might mean re-reading the file list.
As others have mentioned above, keyboard operation is
essential, so I'm pleased to note your commitment to it.