I didn't got the device on a contract but as a prepaid package, so I bought it cash together with a Vodacom prepaid SIM card.
With Vodacom you can signup for the Blackberry Internet Service by using your airtime, R59 for 30 days (subtracted from your airtime) gives you unlimited Internet access e.g. browsing, Facebook, Twitter and push email. Note that Skype (VOIP) or any form of streaming will cost you extra since that isn't part of the unlimited Internet package.
For push email you just register your email addresses on the Vodacom portal and get pure push email (I will blog about push email in the future).
For Facebook a little blue envelope will appear if someone sent you a message etc.
The Blackberry Curve uses GPRS/EDGE and Wifi unfortunately no 3G support but for me that is fine since I'm mostly in a office where there is Wifi and yes I'm one of those that don't use my phone while driving.
For me the most to get used to was the little keyboard, I came from my Samsung Omnia i900 and iPod Touch that got touch screens and all of a sudden need to get used to the little keyboard.
If your a developer, please fill in my poll: Do u want C#/VB.Net for Blackberry?