For those of you waiting on the edge of your seat for the resolution to this story, it is this:
After over an hour on the phone with someone at Dell, I was told they'd send me a new monitor. Two days later I could see by Fed Ex tracking that the device was on the truck in my neighborhood, when Dell suddenly cancelled the shipment! Grrrrr! Apparently they wanted more proof of purchase, even though they didn't think to ask me for it until the very hour that the shipment was due. It took another week, and conversations or emails to four different parts of the company, for the replacement to arrive.
Lessons learned:
---stay away from Dell
---do not allow service people to send me to another part of the same company for information. ("To find out when your product is to be shipped, call this number or email this address....") You work for Dell. You find the answer and tell it to me.
Long story short, new monitor looks just the same as the old one. In Adobe RGB, there is still no separation in the blacks and near-blacks. I returned both monitors.
The unresolved question: Am I being unrealistic to expect to see a full grayscale in Adobe RGB on an LCD display?