Anyone have any experience with tethering iPhones to use the internet?

I'm moving into an apartment closer to town on Sunday, and I'm going to need internet access for uni.

I thought I'd give tethering a try, before making the decision to get internet connected. My iPhone is with Vodafone, and I get 500mb of data included each month. 500mb seems like a lot...I'm on the net for probably about 1-2 hours each day on the iPhone, and I only use 30mb per month. But I don't know if 500mb would be enough once it's connected to a laptop.

Thoughts?

If the tethering is a bad idea, then what is a good cheap-ish broadband deal that I can get? [between $25-$40 a month] Internet at my parents house is with Internode, and they seem fairly good?