How do I use the Round weapon in Space Invaders Infinity Gene effectively?

I am having difficulty getting the hang of the Round weapon in Space Invaders Infinity Gene. While the "bullet eating" effect is handy, I'm not sure how best to use it in general because of the way the bullets shoot from behind the ship. If I want to shoot an enemy coming from the upper left of the screen, I have to move my ship towards the bottom right in order to shoot it. Should I just be constantly moving my ship in a little circle? Is it just a matter of practice and fine-tuning? What am I missing here?

I'm playing the PSN version, so I'm using the joystick controls on the PS3 controller, not the iPhone version, where you can use touch, if that makes any difference.

The round weapon is by far the most difficult to handle. It is counter intuitive since your weapon fires in the opposite direction that you last moved. It is also very useful since you can fire 360 degrees and attack from safely in front of some of the bosses. Try to use quick sharp movements away from the direction the enemy is attacking from and stay still whilst enemies run into your line of fire. It is almost impossible to micromanage this weapon so just dart away when in danger and you will now be firing at the exact place you were about to come to grief.