In fact a guy passing notes between the cables might be faster and more stable. j/k
That really isn't too far from the truth!
Can't argue with any of your points, its jut not the easiest solution. 99% of users will never need more configuration than is available with most new routers with up-to-date firmware and most won't want to mess with all the setup.
Personally, I wouldn't mind setting one up and learning about it, but my time is valuable. A lot of people aren't going to want to sit and learn Linux or new commands/protocols. Consider the several hours spent reading, setting up and coming back here for questions to get it right vs. $79 for a router and be done with it. Once you divide it out by the hour, I'll bet you don't save much $$$.
Besides, I can always find some better use for a box whether it be backup storage, loading new software or OS's to learn so I don't screw up main systems... whatever. That stuff is worth more than $79 to me.
Anyway, we are way off the point. This is really not an argument about the best way to setup but rather a whatever floats your boat question.
[edit]
I just read the manual for that software. It is pretty cool. But I'd still rather have the ease of a router and use the box for something else.