I love using mini-kegs. I have a Philtap system. Together, it's great for a couple of reasons in my case. I don't have a lot of room for more than one corny keg, but I can fit three or four mini-kegs in the garage beer fridge.
You can force carbonate with the Philtap. It works great, imho. I love taking my beer to family and friends houses for parties. It's way more portable than bottles or a larger keg.
And like the other poster said, you can reused the German 5L kegs, (not Heineken), so you can buy them, enjoy something you don't normally drink, and reuse the keg.