With power like that you'd do well to set a minimum difficulty for that worker. For a 700GH unit I use a minimum difficulty of 256.
All this does is make sure the big units chew on the harder stuff, but it kinda stops them getting clogged up with easy stuff. Apparently this helps with payments.
No doubt DrHaribo can clarify more.
It doesn't really help with payments. Higher difficulty means you use less bandwidth (less network traffic), but also your variance will go up. That means the daily variance in your earnings will vary more, depending on your luck in finding proofs of work, than if you had a lower difficulty.
The mining server will automatically adjust your difficulty to a level that is a good trade-off between bandwidth usage and variance. Normally it starts you on difficulty 4 (currently) and ramps up the difficulty from there. By setting a minimum difficulty you can make the first minute or two of mining smoother by starting directly at a difficulty that fits your miner. The minimum difficulty is also useful for broken mining clients (like on the Dragon ASICs) that use a difficulty from their web interface configuration and ignore the difficulty the server is telling it to use (a complete violation of the Stratum protocol). In this case make sure you set the minimum difficulty for your Bitminter worker to the same difficulty in the Dragon web interface. Otherwise you may lose most of your work and mining income. And/or ask the manufacturer to repair their software.
General advice, set your minimum difficulty to your hashrate in GH/s divided by 1.4.
Info on difficulty, work submits per minute and the easy mode perk:
https://bitcointalksearch.org/topic/m.3142713
