I love this huge mat for my Slice machine. The one that comes with the machine is nice for cutting out one or two shapes, but then requires that you remove them from the board so you can do more. I love that I can lay a full 12x12 sheet of paper down here and cut a whole title before having to worry about lifting the letters off the mat.
I just wish that it came with some kind of cover to put over the sticky mat, so that I wouldn't have to worry about dust and such. I store my mat in the box it came in, but that's big. I'd love just a small piece of clear flexible plastic or something that I could lay over it (similar to what you see with the Cricut mats).
The storage issue aside, it's totally worth the money!
Since the Slice is easy to position where you'd like it...this mat is a GREAT way to make sure you're getting the most cuts out of your paper. Take a bit to get a handle on how it cuts - some of the flourishes, etc. cut on the diagonal. Once you have that down, tho, this is the thing to have!