I've got experience. I've tried it twice and each time was different.
I think they make a great reuasable (to a certain extent) cask system.
Also, a friend uses them with a portable CO2 charging system (BB gun cartridge and ball lock adapter). The CO2 helps to keep the beer fresher and hold carb better. There is a limit to how much pressure you can put on the keg fittings, but it works well enough.
When I did it I simply filled from the keg and planned on drinking that day/weekend.
While they work fine in a way, they are not a direct replacement for a real kegging system.