Another bump.
I've just finished upgrading my cabinet with 12 of these Ultimarc leaf-switch buttons, replacing the generic microswitch buttons the cab came with.
As has been said before, these do not feel the same as standard leaf-switches. They're very, very light in operation, and don't have a strong spring-back.
However compared to the microswitch buttons they replaced they're quieter and incredibly responsive, and make a huge difference in games like Defender or Joust where speed of firing is essential. They're also much less tiring on the fingers, due to the low actuation force, and you don't need to fully depress them to activate them.
For games like Asteroids which are played entirely on buttons they feel much more authentic than microswitch buttons.
On the minus side, the connectors are tiny and flimsy - I was concerned I might break them. I didn't want to have to re-crimp all my wires, so I had to bodge my cabinet's 4.8mm connectors to fit.
They were slighty shorter than the original buttons. but I had no issues with sizing, as they fit just about perfectly in my wooden panel. They take up much less room than microswitched buttons, which makes them easier to wire up too.
Overall, I like them a lot. They're a great alternative to microswitched buttons, especially if you don't have the room in your panel for standard leaf switches.