I love my AccuQuilt Go! and Sizzix Big Shot. I do a lot of scrap quilting using fabrics from thrift stores and estate sales. And I make a lot of baby quilts to donate, so it seemed like a die cutter would help me finish more quilts than I could if I was cutting them all with a rotary cutter and ruler.
I can't tell you how much fun I've had with these machines over the past couple of years.
I've used my Go! to quickly cut enough units to piece a two-color Drunkard's Path quilt while I was recovering from knee surgery, to trim someone else's unevenly cut squares so that they were all the same size. It's great for cutting things that would be time consuming or impossible with a rotary cutter and ruler.
When I've just been in the mood to play, I've experimented to see if I could use the Apple Core die to make Halloween bats, or the Dresden Plate and Drunkard's Path dies to reproduce a traditional pieced turtle block. The more ways I can find to use a die I've purchased, the happier I am.
I've used my Big Shot to cut intricate shapes that I just don't have the talent (or time or desire) to cut by hand with an Exacto knife. There is no way I would have cut all of those typewriter keys by hand -- not when I could buy a die for ten bucks that would do it for me over and over!
Depending on what shapes I'm cutting and what fabric I'm starting with, I also love the Easy Angle Ruler and Companion Angle.
I also use template plastic, or even cereal boxes, if I want to make something that I don't have a die for, but I sure do appreciate what I've been able to do when I've got the right size die or ruler!