They are a great idea.
I use them for continuity testing, as they make it easy to connect to a long wire.
Some times however, they do not fit where the probe needs to go, and they have to come off.
This is where they get lost.
I wish there was some convenient way to store them in the multimeter itself.
perhaps a probe with some sort of latch mechanism. it would be great if you could just push the probe into the multimeter to click it on, and push it in again to get it off, retaining it inside the meter.