I didn't have any issues with my Samsung Blackjack - or maybe I just got used to it. My main complaint was that it was 3GSM only and didn't work in Korea or Japan. So I asked my company to upgrade me to the BlackjackII, which I hoped would give me a nice upgrade along with its quad-band functionality.
And my impression? Hmm, so-so. Not really all that different from the BJ1. They replaced the flywheel on the side with one on the front, which I was initially excited about, but I ended up not liking. It is too "slow" and they don't provide a way to update the speed (imagine using a very slow mouse with your computer and not having the ability to adjust its speed).
It has a nicer "surface finish" than the first generation and looks more stylish, which makes up for its slightly thicker size and a few extra ounces.
The updated Windows Mobile 6 is nothing to write home about, and the internet connection seems slower to me than my BJ1.
Overall it's an okay phone that I will be happy to be using on my trips to Japan and Korea. It isn't a blockbuster, but maybe that is because the iPhone upped the ante.