I posted in the testing thread as well. I have an iPhone 4 on IOS 5.1, Quicktime 7.7.1 and Windows 7 64-bit. So far I have been able to view the files on the iPhone and transfer from MediaMonkey to the iPhone successfully, including the artwork. Great work, guys.
I am no computer expert, so there's nothing fancy about my setup. I have just followed directions. I have done some Media Monkey beta testing and have had some problems in the past, so I haven't had a perfect track record with testing upgrades. I am very happy that I will once again be able to abandon iTunes, which I have only half-heartedly used in the past.