We're pretty keen on Globalgig's Roaming SIM card, which is one of the better-value offerings for travellers out there who want to dodge roaming rorts. Now it has an added attraction — an option to access 4G networks in Australia and the UK, which is actually one of the cheaper 4G data packages even if you never head overseas.
As Fat Duck Tech notes, the addition of 4G (via Optus in Australia and through 3 in the UK) has also seen the pricing for the service revamped slightly. The new plans include an Australia-only option with the following prices (all deals are month-to-month, and excess data is $0.02 per MB):
If all you're after is data, that's a pretty good deal — 10GB for $50 is easily as good as it gets for 4G broadband. If you do want to make actual phone calls, then other prepaid Optus network options (Amaysim, Jeenee, Vaya or Virgin Mobile, as well as Optus itself) are still worth considering, though none have such high data allowances at the top end.