I was walking past Hollands the other day and they had brew dog growlers on offer. €9 gets you a growler and €18 get you a growler and a fill. You get about 2.5 pints and isn't totally flat when you drink it...
Problem is that they are filling them from the tap and it means that if you do not use a tube and fill from the bottom up, that you are left with a big dead space that the gas leaks out into.
Having said that the guy reckons that they are committed to the growler route and the plan is for them to have specials (cask & keg) in the off-licence only for the growler trade.