They are excellent.
I bet if I was racking almost any piece of Meraki kit I could do it in half the time of someone using cage nuts, and I wouldn't have any bleeding hands or fingers when finished.
Let me do one call out to Meraki though - Why of why do the MX84 and MX100 only have a single rack mount fitting each side instead of two, like everything else. You need two each side if you want things locked nicely into the rack. Please put two rack mounting holes into future models please.