I have two Reed Geeks - the 1st edition, and the new Bullet. They are both very well made, and they do what they say they will do. Having said that, I think I tend to buy things that look cool but that I don't really need.
I also have a couple of 3/8" High Speed Steel lathe tool bits that I got on Amazon for about $5 (they came two to a pack). I call these the "cheap geek". For flattening the back, they work just as well as a Reed Geek. They don't have the curved cutout or the radius "eraser" on the end that the real Reed Geeks have.
I have tried using the "eraser" for adjusting the tip, and the curved area for adjusting the side rails, but they don't work as well, **for me**, as plain old 320 grit sandpaper with the reed on a piece of glass. I do flatten the backs of every reed I use, but I tend to use the "cheap geek" for that as it's a little bigger and easier to use.
However, if I were a touring musician (those days are gone...), I would take the Reed Geek with me instead - the lathe tool bits have an angle on each end, and the edges are sharp enough that a TSA agent might confiscate them. The Reed Geek will pass TSA inspection. That's worth the extra $40 or $50 they cost.