I got the GO! for Christmas last year. I picked up the charm die and a few others came with the bundle my husband purchased. Personally I love it. It cuts my fabric cutting time down, it always gives precise cuts, and I can't wait to use it for applique.
I think if you do a lot of applique quilts, it would be a fabulous investment, but if you work with precuts or quilts that require a lot of different templates per quilt (like paper piecing) then it's probably not worth it. For me, it was worth it just to get the 2.5" binding die, I hate cutting binding. lol