I tried using mine for cutting the pieces of a block of the month quilt once. It seemed to work great, but when I went to sew the half-square triangle pieces together, sometimes they were off by 1/8” or more.
I read that you need to be extra careful with grain lines. Mine was a gift, so I admit to not investing the time to learning the proper way to use it. I am pretty set in my ways, so I’m not the target market for it. 
With that said, it’s easier to use than a rotary cutter and ruler for people with arthritis or when stability is a concern. I imagine it would be wonderful for curved pieces.
Try cutting only one layer at a time at first, then measure the pieces to see if it cut them correctly. Make sure you use the mats on top of the dies.
A lot of people love them, and they seem like they are made by a good company, so your experience may be better than mine.
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