A few weeks ago, I was given a big bag of 3" squares. I use 2 1/2" squares for most of the baby and lap quilts, so I've been cutting them down with my AccuQuilt. I've been burned in the past by assuming that sets of squares from thrift store bags would be accurately cut. This way I know they're close to perfect, and it also gets rid of the frayed edges.
While I had the cutter out, I also cut a couple of birds to see if the project that leapt into my head at two am will work by the light of day.
Here's a short video I put together showing how fast it is to retrim squares with your AccuQuilt. I've done it before with my rotary cutter and ruler -- it's much easier to just lay the fabric on a die!