I recommend the blackberry especially if you work in an office/corporate environment. It is much more standard.
Blackjack does great and has enough features to keep your attention. BB is a workhorse but requires you pay extra money for the BB service. All depends on your needs. I would get the Blackjack since it does most of what the BB does without the extra ...
stay with samsung and try the D900i or the G600 both of these phones are very good i up-graded to the D900 after my D600 and i am very happy with it and have had no problems hope this helps