I use a Therminator and love it. I would have no problem getting wort down to 68*F in one pass, but I would use a lot more water pressure and the wort would not be coming out very fast. Because of this, now I use very little cooling water and recirculate back to the kettle until the whole thing is where I want it. I have a Venturi set inline so I get aeration during this recirculation. This system also allows me to swap up my cooling water lines to another pump that sets in a ice chest for further cooling in the case of brewing a lager. I use a lauter grant for my mash tun, so when it is time to collect the boil I use the same grant (this is because it is actually combined to my pump).
I simply attach my filtered funnel to the grant's top and let my kettle drain hose run into that prior to the grant/pump/Therminator/Venturi aerator device/back to kettle. This catches a lot of break material once the kettle starts cooling, but continually collects particulates and protein formations right from the start. When the filter gets filled, usually 2-3 times in my case on a 15 gallon batch, I simply shut off the kettle valve and clean the filter. Takes all of 30 seconds with a bucket of cleaning water and a dip in Star-San, then I am back to chilling and aerating. I love that I get to grab the most cooling power out of my water (actually the most heating power is how I look at it, for later cleaning). I keep my chiller clean this way, and I get cleaner wort for it as well. I have tried many combinations, but this one has been the most successful to date.
Still, the plate chillers are awesome! If I didn't have ulterior motives for the chiller water and aeration while chilling, I would be 100% confident in one pass chilling with this bad boy. But... always, always, always, filter if you have a plate chiller!!!