I used to use one when I first started prawning. With 400 to 500 ft of rope, 2-4 traps and 10lb cannonball, it took approx 30 min to retrieve everything. Good system for what you pay (when next cheapest option is to pull up manually). You may be able to fabricate some for the same cost range with a windshield wiper motor.
My boat has twin 200hps, so gas during this trap pulling was not relatively cheap (outboards in idle during whole procedure).
Anchor Lift's effectiveness is based on the amount of drag created by buoy (the bigger the better). Size A1 is bare minimum, A3 and bigger is good. I rigged mine with a sea anchor (10 gallon pail with bridal just as good) attached to Anchor Lift to creat more drag. Rope did not slip with proper rope diameter (5/16"). The toggle in the mechanism seemed to bight down pretty good.
Things to be aware of: tearing traps off or snapping rope if snagged on bottom while driving away. Sometimes it was difficult to tell if snagged. Traps could blow off if driving away too fast or when the trap snap collides with the Anchor Lift.
I was happy with it's performance for it's price, but have since invested in an Ace Line Hauler. Which is great for the price of an electric downrigger. It's like converting from a manual rigger to an electric.
Just my view and opinion.