I'm surprised so many people commented on the weight of a Mamiya TLR system. While I find using it handheld to be clumsy due to the size and apparent topheaviness of the C330, I've never been bothered by the weight of the camera. I have a C330 with 55, 80 and 135 lenses and the bag with this system plus film, filters and extras is really lightweight to this overweight, middle-aged photographer with a bad back and neck.
Conversely I find the weight an asset when handholding as the thing doesn't shake as much as my EOS 35mm. Much steadier in fact. I suppose that should read, I don't shake so much with the heavier camera!