I have the earlier version of Mark's keg washer. It is slightly larger with a 3 gallon reservoir. For me personally, I would like to see a slightly stronger pump, and some side jets that hit near the typical krausen area. I guess if you let it circulate long enough it might actually get these areas clean just from the continuous action of the solution running over the krausen, but I think side jets hitting that area would be more effective and quicker.
After using it once or twice and seeing how slowly it was cleaning along the krausen line, I permanently changed it over to a sanitizing vessel. I purchased some saniclean, which is basically starsans low foaming sister product, and I keep the reservoir filled with that. I sanitize all my kegs and carboys with it, which it is quite effective at.
For cleaning I still just soak kegs and carboys over night with some Oxyclean, then flush them with fresh water. I have seen many DIY keg cleaners on line that have more power and mods for side jets, and if I ever get the time I may build one so I am automated for cleaning and sanitizing, but for now it is nice to just pop a carboy or keg on the Marks Keg washer to sanitize, and walk away.. At least I'm half way there. Your mileage may vary.