I was at the ADA Expo in Seattle last month (April) and met an Abbott rep who told me that it was mostly not the FDA but a financial decision. He said the FDA did have a minor problem with the sensor manufacturing plant but that it was mostly just the US market was too small to make a good profit compared to the European market and they chose to make more money. He was very emphatic that Abbott has not given up on CGM and had newer stuff in the works (he had no details) and they would wait for the third generation (second gen is what's in Europe) to reintroduce back into the US. Of course we all know that it could take forever because of the FDA so don't hold your breath.
The longer I use the Dex the more I hate it! Although my A1c is roughly the same I do have wider swings and many more correcting boluses and glucose corrections. There is only 3 things I like better with the Dex, one is the size of the transmitter, but I'd prefer the larger Nav in order for the extended range. Second I like the Dex inserter, it's a little easier than Nav. Third, resetting the receiver to fool it into a accepting extended sensor use. In every other aspect the Nav is vastly superior for managing Bg! I guess it's better than nothing.