Think about it.
Simple Finder is proof positive that Apple is quite capable of producing absolute cr*p. I wasted several hours of work experimenting and learning Apple's undocumented Simple Finder, only to realize I could create files in SF, but I couldn't delete them.
Simple Finder in OS 8 was an important addition to the OS. In OS X it's an blight, a festering sore, a sick joke on Apple's customers. (Can you tell I'm annoyed?).
My mother's Mac Mini will run Simple Finder -- at least for a while. I've been experimenting with SF and, if one ignores the official way to configure it and uses the 'Full Finder' configuration method
So now I'm looking for a Spotlight front end. I searched on one I've licensed (MoRU), that led me this post where the comments mention a few others : Hawk Wings: Two apps for a smarter Spotlight. I'll also play with Launchbar and see how that will work -- but a simple Spotlight front-end that works with Simple Finder, and that can be constrained to only search Documents, is what I'm looking for. I'll see if I can configure MoRU to do that.
 My favorite technique for finding good reviews of a class of products is to find two product names, search on the two together, then find three, search on the three together, etc. Chances are a review that discusses 2-3 competing products is a genuine review, not a fake.
Update 12/12/06: I tried creating a smart folder that would emulate a spotlight interface, using the trick of defining the smart folder to show all files created in the past 99 years. Alas, smart folders are inert in Simple Finder. Then I tried MoRU ($10). It works pretty well, and with a bit of tweaking I was able to create a simple interface. It even supports zooming the UI. So far MoRU is looking like a good bet, but I'll try a few others.