I live in Canada, so this phone works on the Bell network so I can't say whether it is the 4G version that the AT&T users in the US have, but I can say that this phone rocks.
I will admit that I was a little skeptical as I quite enjoyed my iPhone. The quality of the phone was top notch, the apps were great and it was the best thing since sliced bread. There were things that bugged me about the phone though, it seemed that the apps were limited. They weren't built to fully replace a computer, I also had an iPad which was a huge disappointment for me. Not a business tool and really no better than a phone.
Enter the Atrix into my life. It has power to spare and Android has impressed me. I have always been a Google products user, gmail, Google Docs, etc. The integration between the Google products and Android is amazing. This is the phone I have been waiting for. It harnesses the power of the cloud provided by Google (the honourable cloud masters), provides flexibility to customize the way the phone operates (which Apple would not allow for), and gives an amazingly powerful phone.
My friends are constantly amazed that I didn't get an iPhone 4, but I will never look back. Granted I have always been more technically inclined and I really like to play with the look and feel of the phone and optimize it for exactly how I like it. But my wife also got an Android phone (LG) and she is very happy also.
If you are looking for a opinion about Android, mine is a glowing impressed opinion. If you are looking for an opinion to see if Motorola still has what it takes to play in the phone world with Apple, mine is that their latest edition to the line up is the best phone out there.
I haven't even tried the peripherals yet. If I could only convince my wife that I needed the lapdock...