The Sierra AirCard 860 works great here in the US on Cingular's HSDPA network and Cingular is currently the preferred option of the service provider's two cards because it gets slightly better results in areas with weak signals. The Novatel U730 is by far a better card. If you are planning on Using it in South Africa ... there really is no point, its going to cost to much and the service is not going to be great.
I've managed to get my hands on an AC860 here in South Africa, and I've been trying to get it to work on the vodacom network all morning. It only seems to want to connect through GPRS though. It doesnt seem to think it can connect to VC on 3G/HSDPA.
I hope the cards 3G/HSDPA frequency bands are compatible with what is available in SA.
I just stepped out to get a VM sim as well, we'll see if I have better luck over there. If GPRS is going to be the best speed then I might as well use it at a cheaper rate.