I went and saw the blackjack tonight and asked that question and the salesman said yes. He also said it probably will work fine with pda connect but they question if they see high usage. Otherwise they wouldn't know. And yes it will tether 3g.
I haven't tried it with a pda plan but last night I got it working with a straight dial up connection. Cingular connection manager doesn't say it's compatible, plus I tried anyway and it wouldn't ever detect the phone. I ran the cd that came with it, said "install samsung modem driver" clicked it.. always got an error saying it was already installed. I looked in phone & modem settings, found a "Samsung CDMA Modem".. "cdma??" Anyway.. I guess when I ran the active sync setup it installed it for me after connecting the usb cable.
Long story, I made a manual connection under network connections, just like you would for a dial up.