I started off using a stop with the local mining club.
I did more and more challenging holes until I ended up at Sim's Shaft, Wheal Gorland, which is over 200' with an exciting swing in. My chum used a new rope and didn't need to touch the handle of the stop. I used an old rope and found, rather alarmingly, nothing happened, no matter how hard I squeezed the handle....wait, I'll try and feed the rope through...nothing, nope, I'm stuck, yep stuc............aaaaaaaagghhhhh!!!! DOYNGG!!!
The whole descent was a combination of this stopping, dropping and bouncing around on the semi-static caving rope. By the time I got level with the shaft station and needed to lock off, it was red hot, so much so, I burned a shiny patch into my hand.
I went online and bought a Petzl Rack. Job done. It doesn't matter if I have 400ft of rope below me or 40. It is totally and utterly smooth. So much so that I don't have to focus so much on my descender and can note my surroundings, hazards, etc.
I would never ever use a stop and the only positive I can see about them is that they are small for going through gaps. Some other chums all use ID's and I've dabbled with these and if I needed something fiddly for horizontal fiddling and macrame style rigging, I'd buy one of these.