Ok..
It has a valve you can attach at the bottom for the acclimation process and you adjust it for the drip speed you want. Well that valve turns 360 deg, and even if you could adjust it underwater which is very difficult the knob has next to no gripping surface, you wouldn't have a feel for it. You have to adjust out of water, the moment you do, water from the unit is now dripping into your tank. (try and adjust before placing in the tank so lfs water can't get into your tank)
The tubing for the valve is quite stiff (i should just replace it) the slightest bump and the valve falls off.
That's enough to make it a PITA, but its nothing that is hard to fix, I may replace the piece of hose and try an airline valve or anything that is easier to grip.
I have used it to house brine shrimp for the weekend, with an airline connected where the valve goes, due to the poor fit of the valve hose I didn't use it just airline directly to it and a knot in the line to control pressure. It worked fine but very noisey with air bubbling. Due to the way it mounts it has lots of room to rattle and loud.
Could be a better product with some refinement. Maybe the grass isn't greener for the reef gently unit... or mebbe it is...