I've run 3 different ones at various times...
The trick to these overflows is to run them between 60% and 80% of their rated capacity.
If you run too little flow through them, bubbles accumulate in the top of the overflow and will eventually break siphon (that is, unless you use the aqualifter). If you run over 80%, the overflow has a hard time keeping up. I've found their ratings to be "optimistic."
If you do get one, the two pieces of advice I'll give you is first, keep a spare aqualifter on hand at all times. They need to be replaced every 6-12 months. Second, use black hose on the aqualifter. Clear tends to jam up with algae. You can get black hose from a home improvement store with the "drip style" sprinkler system stuff.