I discovered a problem with my set that was causing it to drift. I would set it correctly and within days, sometimes less, it would shift the grayscale and peak brightness. If I had used a pro-calibrator who was a of national reputation he would have come in cablibrated my set, took my money, and he would have been down the road. Now if he was local be might have come back half a dozen times for nothing (assuming he was a really nice guy) and figured out the problem.... yeah fat chance. It just was not obvious and I can't even imagine trying to get the maker's customer service to do anything positive about it.
I have been messing around for months going through one Duo beta after another recalibrating my set anyway.. but the problem with my set is probably either a hardware problem, a bug, or an undocumted feature. It literally turns down the brightness apparently when it gets to a certain temp on the lamp. How did I figure it out.. well you know what you get when you don't get what you want... in my case lots of trial and error experience.
So while thank goodness for great pro-calibrators, unless they are local they have some limitations on what they can achieve if there are gotchas. The nice thing about a Duo, is with a decent meter and some persistence you can achieve over time, what a pro can not always achieve, they just can't make that kind of investment of time in your set. I have to give some of the great ones credit, day after day, they have to be able to wade into a deep pile somehow and turn it into a silk purse. In my case the efforts of a traveling pro no matter how brilliant would have resulted in a Cinderella effect. After midnight it was all going to turn back into the pumpkin.
The Duo still has warts, but for the money it is an awesome piece. I would buy a couple more of them if I had a few extra bucks around. I have a couple of Panasonics that simply don't have any real adjustability. One gets used as a PC monitor so... it's not important right now, and the other just doesn't get a lot of use. Still when they (Anchor Bay) do the 3 hdmi port "Lite" version for $499, I will stick one on every display I own.