> If I offer to turn them off they often get surprised at how much faster the phone feels after.
If you're using Android there's also a "visible touches" option you can turn on in the Developer settings. It's a big UX enhancement of its own and IMHO should be promoted to the Accessibility settings (together with the options for speeding up or disabling animations).
It provides a quick feedback loop when you're trying to poke at stuff on-screen with your fingers. Which is nice since it lets you know quite seamlessly (1) how good your aim is, which gets kind of critical when using fingers on a touchscreen compared to a mouse. and (2) whether a tap has even registered in the first place, which is often problematic for many users who may be wearing gloves, have drier skin that doesn't register as easily, etc. etc.
If you're using Android there's also a "visible touches" option you can turn on in the Developer settings. It's a big UX enhancement of its own and IMHO should be promoted to the Accessibility settings (together with the options for speeding up or disabling animations).