[davidmanze]

Dave I think you attributing some mirror related shortcomings to the shutter:
1) shutter sound although audible is minimal, the sound you hear from DSLRs is the mirror flap, my EOSRP uses a mechanical shutter, it is barely audible.
2) shutter mechanism is rather fast, it is the mirror flap limiting the frame rate on current SLRs, of course electronic shutter is faster than a mechanical shutter, but it isn't the one limiting high FPS for the time being.

  Actually, I wasn't attributing shortcomings to the mechanical  shutter ..... the contrary, I was attributing shortcomings about the electronic shutter .......... (rolling shutter/banding) .... most field sports situations aren't that noise sensitive and as you say without a mirror the noise produced is relatively insignificant ....
........ with the announcements of Nikon, Sony and Canon's intentions to produce a truly professional sports mirror-less camera ....  I see them looking to have equal frame-rates mechanically and electronically .......... 
........ then you have the best of both worlds!

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OT  ...... Eddie Van Halen ...

   I'm not a heavy metal dude and know little of their music ...... but with all the utubes coming out of the woodwork .....

What a great guy with such a precocious talent  ....... RIP