I've seen those pacsafes for sale. They don't seem as secure as I would like them to be, but I guess they would be OK for the grab-and-dash kind of theft. Wouldn't simple tinsnips make short work of those wires?
Actually the PacSafes are quite secure. I think one would have quite a job of cutting into one with tin snips. It would take cable cutters. (Cable is difficult, verging on impossible, to cut with chain/bolt cutters or a hack saw.)
I use the PacSafe day pack to secure my camera gear and laptop. They also make a duffel bag version.
(The 'chicken wire' thing that goes over a regular backpack - don't go there.)
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As for gear size/weight. I'm carrying a lot less now with dSLR, lenses, and PHD than I did with fSLR, lenses, and dozens of rolls of film.
My battery charger is about the size of two rolls of film. My PHD, about the size of four rolls of film.