Using Parallels I recently installed the Verizon Modem software that allows the BB to act as a modem with internet access. It went a smooth as eel snot.
This is a Windows application and it is not available from Verizon for the Mac.
This allows the Windows side to work on-line. The Mac side cannot see the modem.
I got on the Parallels web-site and they have detailed a procedure to change IP adresses and some Parallels settings to allow the Mac side to see the modem.
Does it cost extra for tethering you phone to the mac or other computer?
If you have an unlimited data plan with your service provider, in theory it shouldn't cost, but small print says theirs a fair use policy of x amount of gigabyte limit which varies from different providers.
I think mine is 1 gb per month. But the speeds I get, I highly doubt I'll ever get anywhere near that amount of usage. I don't use it for downloading just general surfing.