not being sealed is a PITA - I have the morebeer one, and when you get the flow started, its quite a balancing act to get the wort flowing through fast enough to not lose prime on the pump, but not too fast that it starts seeping out the loose lid. Its not turrible once you get the hang of it, but it ain't ideal.
I may have to look at the hop rocket, especially since I am switching to boilermaker kettles anyhow.