I will say this though. I have one I bought a decade ago for my router table and I love it, but for a tool like a miter saw that's a lot of really short on-off cycling of the switch and the vac, and neither are really made for that. I've seen a lot of complaints of failures of an auto switch when used like that. They are really designed to be used with tools like a table saw, band saw, thickness planer, router table, etc than they are for something like a miter saw that will only run for a few seconds at a time.
[Edit: Now that I think a bit more about it, it would also be awkward to use on a miter saw because you would need to pull the trigger on the saw and hold it a few seconds for the switch to turn the vac on and it get up to speed before making your cut. That would just plain drive me crazy. ]
I would suggest that a remote switch for the vac may be more practical and reliable in the long run.
https://www.google.com/search?q=fastcap+remote+Vacuum+Switch
<iframe width="560" height="315" src="https://www.youtube.com/embed/8U-BFDSxy4Q" frameborder="0" allowfullscreen></iframe>
