I'm brewing a Helles tomorrow. Normally I'd stir up a 2-2.5 liter starter for the beer but, since Thursday was Homebrewer's Night at the local homebrew store, I got home too late to stir the starter up, boil it, cool it and pitch the yeast. Since I was at the LHBS and noticed they had cans of Propper Starter, each good for a liter, I picked up two. At home, I sanitized the flask, opened the cans and poured them in. Diluted with equal parts water, it made a 2 liter starter. I smacked my yeast, dumped it in, put the aluminum foil over the top and started spinning. Now there's a nice white layer of yeast on the bottom of the flask and I'm ready to brew tomorrow (with the slight underpitch). I won't be buying it all the time. It's rather expensive at $5 US per can, I could hypothetically make sweet (unhopped) wort and freeze it but then the time savings are gone thawing the wort and I'd have doubts about sanitation, leading to boiling and cooling. So while it was nice to use in a pinch, I won't be using it all the time, I'll keep stirring up DME when I need wort.