Re: planning to buy a new mobile phone.
^ That is correct, does not work on prepaids... I was in Pakistan recently and the Bberry features worked flawlessly with both Mobilink and Ufone postpaids (on 2G though), didnt get to try the others. Tethering works too, though it takes a little bit of doing. If you want to skip the hooplah of getting a post paid line in Pakistan, you can use your BB features through your Wifi at home (assuming you have that), and everything including the Bberrymsnger would work. Be warned though, Bberry registration on your prepaid phone might shut off all bberry services except the hotspot browser, until you hook it up again to a bberry package enabled SIM.
In the US, from what I know you have to sign up for the Blackberry Data Package. I forgot how much I pay extra for that but its around $30 to $35, on top of your plan and any messaging bundles you might have.
Crackberry4eva!