See a bit about the quick trim ruler with this video link. It was posted from creative grids on YouTube.
I wouldn't use the quick trim ruler for lots of circles. For lots of circles I like to use the Cut-A-Round ruler. To the left is a picture from Sara in Sioux Falls, SD with a demo on the Cut-A-Round. I like it much more than the "circle cut" ruler. It is harder to find but worth it. I know you can order it from Sara at Heirloom Creations in Sioux Falls SD if you can't find it local. The reason I like it so much is because it is designed to have the fabric folder in quarters. When cutting a circle the shape of this ruler makes it much easier to fit a rotary cutter into than the more common Circle Cut ruler. Give this one a try if you like making circle quilts.
It comes in a few sizes to create about any size circle you would need.