If price is no object and you're a speed junkie, then the newly-launched Telstra Elite mobile broadband card is an attractive 3G broadband option, squeezing the Next G network to offer (theoretical) maximum speeds of up to 8Mbps in capital cities. It also offers quad-band access, making it a more sensible choice if you plan international roaming.
The downside? Your notebook will need an ExpressCard or PC card slot, which are becoming rarer on many notebook models. And as ever, you'll be unlikely to see those maximum speeds terribly often.
The card can be purchased for $399 outright, or subsidised with a 24-month contract on one of Telstra's business plans. (Note that, unlike the recently revamped consumer Next G plans, these plans do attract excess data charges if you go over monthly limits.) It works on both Windows and Mac systems.