From what is posted at WMPowerUser.com and eventually on Mobile Review.com, HTC Mega, one of the first devices to launch with WM 6.5 is running build 21843.5.0.62. The build hasn't leaked but looking at the performance of 21844 i was sure that it is somewhere near to the release build. But the AKU number is different, 21844 was 5.0.60
And if HTC devices are launched with 218xx builds, then why does the 216xx builds exist? its a bit confusing.
Anyways, watch the videos and read the full review (link on the same page) here :
http://wmpoweruser.com/?p=7450