I suppose the "rattlesnake" won't occur under dim lightning (e.g. inside places of worship, high class restaurants, etc.) where stealth is important. So the problem is not as severe in practice. Agree?
In any case E-M5 should be way quieter than any DSLR. The last time I took a photo inside a quiet museum, the mirror slap was so loud that it alerted the museum staff, and I was told that photography was not allowed. That definitely won't happen with a m4/3 or compact camera (with the beeps turned off, of course).
