If you are trying to make holes for stitching, I think the Sew Easy is pretty cool since it gives you the right holes for different patterns in a pretty fast and easy way, especially if you want harder to pierce designs like curves and scallops. However, you have to buy each head for the different designs.
I keep meaning to play with it, but with my limited stitching that I do on project, I've been very happy with my SU paper piercer and mat pack. I like having a bunch of evenly spaced holes that I can decide on each project what spacing and pattern to use (and I use the tool for setting brads at the same spacing from each corner, etc.) It works for me, but if you were doing a long line or complex pattern, the Sew Easy would be faster.