You'll get the bandwidth quoted, which I believe is around 10,000 GB per month. So figure 20-30MBps, which is very nice for the price.
I have used them and the server was good (solid spec box), the bandwidth was good (not oversold, not overloaded switches etc.) As robwrit says above, you can bank on comfortably pushing ~9000 GB/month. The support was quick, reliable and knowledgeable too. Uptime was solid with occasional planned outages. The only small niggle I had with them was that they bumped the price on me. It went up $30/month over the space of a few months on the strength that they had to upgrade some vital DC equipment.
You may want to contact wdservers here on DP he owns servers at fdc and may be able to get you a deal.