I have been wanting to upgrade my phone since April of this year when Windows Mobile 6.1 was in pre-release. Even months after the new OS went RTM, ATT&T dragged its heels in providing even a modicum of support. Each and every in-store rep was completely and utterly clueless when I inquired once about every month. Alas, I was able to get my hands on the upgrade package for my BlackJack II directly from Samsung.
The upgrade process was pretty straight forward, and for BlackJack II users running Windows Vista, you should have no problems performing the upgrade if you go by the numbers: http://ars.samsung.com/customer/usa/jsp/faqs/faqs_view.jsp?SITE_ID=22&PG_ID=557&PROD_SUB_ID=558&PROD_ID=957&AT_ID=132707%20
There are oodles of new features in Windows Mobile 6.1, and you can find a great feature comparison here: http://www.microsoft.com/windowsmobile/en-us/meet/version-compare.mspx
Kudos to Samsung for doing the right thing for the consumer.