Eddy,
I have been using the soda stream setup to both gas and dispense. Along with some gas used during the flushing of the liquid lines, I've been getting "around" 2 complete kegs (gas and dispense) out of each soda stream bottle. Thus it is only adding around $6 to a brew to go with the expensive soda stream option. But in context, given that at the current rate I'll be going through around a keg a month, $100 rent for a full size bottle each year would still add over $8 a keg just to cover the rent, let alone the gas. Of course if I get into filtering the quantity of gas I go through could skyrocket! Anyway it is early days still, only 5 kegs down.
I picked up a cheap US regulator ($40AUS) which was part of my reason for starting out this way, and decided that I'd want a portable system at some stage anyway. Having since figured out that I'll be kegging the majority of my brews, I've just got to make the decision as to whether I'll upgrade to a big gas cylinder at some stage which will be largely dependant on how many kegs a month I'll go through and how good a deal I can get on a gas bottle (I think there is better options in Canberra than the $100 a year BOC bottles).
As an aside, a gas leak with a sodastream bottle is still at most an $11 loss, and a spare bottle is probably in reach. This might not be the case with 5kg or 9kg bottles.
Cheers, Darryl
