The G1 isn't merely non-silent - the shutter is very noisy and adds vibration, almost like a flip-up mirror.....
Well, your G1 must be a different breed...
While you can indeed hear it (and there is no "silent mode" available), it´s very discreet, far less than a RF Leica. I´d say the noise level is about the same as my old TLR Rolleiflex with leaf shutter, although the character of the sound is quite different.
As for vibration... There are a couple of thin plastic leaves moving in opposite directions, thus eliminating any resultant force. They weigh next to nothing; a mirror weighs several orders of magnitude more, and it moves in one direction at a time, giving a net reaction force on the camera.
I shoot a lot with old Leica lenses on my G1, up to 90 mm (that is the equivalent of 180 mm). They have no image stabilisation, and yet I´ve no problems shooting free hand down to around 1/30 sec, and a fair chance of success down to 1/8. So much for vibration...
If you want a really quiet camera, get an old Leica Digilux 2, and turn off the stupid sound effects in the menu. Even the focus and zoom are soundless. You CAN hear the lens stopping down if you put your ear to it...