The Samsung BlackJack is by the far the best phone I have seen for businessmen on the go. If you have a company that takes advantage of Microsoft Exchange Server and you want a phone that does real-time active-synching this phone is the way to accomplish this.
The phone offers a low-end camera with no flash. I wouldn't advise using the camera too much because battery juice on this phone is not at a premium.
Charging your phone needs to happen at least twice in a 24 hour period. When you are at home or at work. I highly recommend getting a "Samsung" brand car charger from Amazon.com.
The BlackJack comes with two batteries. Use the bigger one if you think you will be using most of the functions on your phone.
Other functions I rated were the IMAPI function setup to access your GMAIL email. It does go out and get your email but some emails do not display.
The Microsoft Exchange emails read just fine and have proven to be wonderful when you are out in the field and need to send an email back to your client.
I have two Blackjacks and my other one has Windows Mobile 6.0 beta and other 5.0. I'm a little disappointed that Cingular and Samsung have yet to release an upgrade for Windows Mobile 5.0 users.
When using the Windows Mobile 6.0 beta I found the calendar function was upgraded and a new function that allows you to send an invite to a user for a meeting that Windows Mobile 5.0 lacked.
In reference to protective leather cases for the blackjack I recommend the one by a company called BoxWave.
All in all the phone has proven to be a great business tool when communicating with my customers.