You guys are a pretty clued in lot, so this should go without saying. Always read the fine print of your contract. We know sometimes you get lazy, or you've been waiting to get served forever and you just overlook it. Well, if you overlook the details of the new pre-paid mobile broadband service from Optus, you could well find yourself out of credit faster than you can say, "Awesome! New movies on iTunes!"
On the surface, the deal looks pretty good: For $199 you get a USB internet key from Optus. Then you can pay $30 for 2GB to use over 30 days. If you need more, there's a range of recharge values - $40 for 3GB, $50 for 5GB, $70 for 6GB or $100 for 9GB.
But this is why you read the fineprint: you get charged in 10MB increments for both downloads and uploads. That's right - 10MB blocks. so if you download a 200KB email in a session, that's 10MB of your 2GB allowance gone. You can chew through the data pretty quickly like that, I would think.
Still having the pre-paid option culd be incredibly important for you, in which case this could be totally worth the money and freedom. Just make sure you read the contract...