I had troubles with king kegs too, so much so that I only use it now as a storage vessel for extra secondary . Usually it's unused.
It's difficult to pour properly, tend to get a lot of foam. The pressure drops off also, so you need to keep it topped up with CO2. I also had a leaking valve on mine the first time, and unless you REALLY crank the lid down you can get leaks there too...
Got a corny though and the difference is amazing.