I've had a great first week with my DX. (I started out calling it my X, but when I told my daughter that I needed to go and play with my X, she gave me a very strange look.)
The improvements in speed, display, functionality and ability to customize, compared to my old iPhone 3G are far beyond my expectations. Of course all of the ability to customize means that one needs to take some time and care learning the OS, and searching out suitable App replacements for the old ones.
Of course with any new device there are frustrations, such as dealing with the odd and undocumented signal bar display switching functionality, and interactions with the screen orientation within a few feet of my Multimedia Station, but now that I understand them - no big deal. The only large problem left for me is an apparent bug which is not allowing me to add a 2nd gmail account, but I'm working around that until hopefully Froyo magically corrects the problem. If it doesn't, I will probably have to try the Restore Factory Data thing.
All in all, it's a great device, and I will never return to the land of Jobs.