Tiffin has been using them for some time now. I find no problems with the kitchen sinks draining, even with small bits of food or salmon fish scales, but the one in the rear shower is another issue. Since we don't shower every day (Boondocking or in a hurry getting to destination) we find the shower drain backs up. When the base gets about 1 1/2" inches of water in it, a stomp or two always opens the drain and it works fine for a day or two. It seems after it dries out well we're back to the pool in the shower pan.
Not really a deal breaker, but a minor annoyance. Seems like a P trap or a running trap would have worked better, and we do have room for either, but the down side might be the possibility of the trap freezing if the rig is in storage and the winterizing missed putting antifreeze in the trap. Of course we winter in the southwest, so that excuse doesn't apply.