Transitioning from Verizon and my old Moto E815 too. Will be really nice to have a new phone, as I've been eligible for well over a year now...
Blackberry 8330 on verizon for black 32gb.
I've switched carriers so many times its redic.
Samsung doesn't make the OS on the Blackjack II, Microsoft does (WM 6.0). I have the same phone and will probably get a 3GS sometime in the fall.
When I upgraded to my iPhone in 2007, I was worried about the same thing. I found that the iPhone was quite the perfect size. It's big enough for an enjoyable smartphone, yet thin enough to fit in a dedicated pocket (I don't keep anything else in the pocket my phone is in) to barely be noticeable. It shouldn't be too tough to accept the change.