Simple circ-saw edge guides rely on the operator to maintain alignment against the guide. The system Chris posted is one of many ways to lock down alignment and make using the guide both simple and highly accurate.
I have guides in 8', 4', 2 1/2' and 1 1/2' lengths, as well as a jig/sled with a locked-down piece of guide for cutting small stuff, which made the 1 1/2' guide redundant. Since the guides and jig are my replacement for a table saw, being able to lock down that alignment is important for consistent accuracy.
In the thread that triggered this one, I wondered about the practicality of using T track for guides. It looks like you've answered that question pretty well, Gene, and other than the cost of T track it looks to be the "perfect" solution.
I just wonder if one were to hit a hidden nail or have some other similar catastrophe whether it would be better to have the saw locked down vertically like that in T track, or if an open track like the one Chris shows would allow the saw to "jump the track" a bit, perhaps minimizing damage to the saw. OTOH, that means a spinning blade somewhere other than exactly where it's supposed to be.
And in reality, the likelihood of such an incident is so slim that either solution is probably as good as the other. I think my perfectionism is working overtime.