How dare you claim a car dealer is stupid.
I had this feature on my 2004 Toyota minivan and used it just about every day. Would love it on the CT, but as noted, hard to find unless you special order. Here's how I used it, however: in the city.
Where I found it most useful was on those surface roads where there are long distances between street lights and 35-45 MPH speed limits. I'd set my cruise at 5 MPH over the limit, then just hang back and let traffic take me as fast as it goes.
On the highways, I'd do the same thing, but set 10-15 MPH over the limit and then I'd go with the flow of traffic. As noted, if you get behind a slow mover, you will slow down (duh). So if you see someone going really slow, you should move over well before you normally would and then the RADAR doesn't "see" them and you don't slow down; you just pass.
Oh the joys of adaptive speed controls...
Honestly, though, people that complain about it being too slow just don't know what a slow car is. Try accelerating from 40 to 60 in a versa or one of those eco cars...it is like hell. Also, they shake uncontrollably!
We have a double-wishbone suspension and while it isn't excitingly quick, just put it in sport for a faster throttle response and you will be on your way.