I have mixed feelings about it.
For cutting straight-sided shapes like squares and triangles and hexagons I have decided it's not worth it due to the waste it creates. Plus using a ruler is so much more flexible, I can cut any size I want, not just the sizes I can buy. And with my June Tailor strip cut rulers and 60mm rotary blade, I am not actually convinced the die cutter is any faster than what I can do by hand - I can cut a lot more layers at a time by hand, and I've gotten enough practice that I rarely make bad cuts anymore. I have gotten a die that was bad and not realized it until I'd cut up a bunch of fabric; now I have hundreds of "squares" that measure roughly 3-1/2 by 3-1/4. (urg) So if you DO get one, I recommend cutting a piece of paper with the die first and measuring, just to make sure it's not bad. (I have 6 dies that cut straight-sided pieces, only one is bad, but it only takes one bad die to ruin a bunch of fabric!)
On the other hand, I will NEVER make a rag quilt again without using a die!! My hands can't handle all that snipping. And for cutting curved pieces like Drunkard's Path I think it's totally worth it, even if I'm a little bit limited on size options. If I ever decide to take on doing a double wedding ring quilt, I will probably buy the dies for it.
I didn't buy a Go, I bought a Fiskars Fuse which is much less expensive. It took a little playing around to find the perfect combination of shims for the Go dies, but now that I have it all figured out it's great.
If you know someone who has a cutter, see if you can borrow it! I was on the fence for awhile and someone on this forum very generously invited me over and allowed me to use her Studio cutter so I could get a better idea of how it'd work, and that tipped me over the edge into buying a die cutting system. (Plus we had a really nice visit - we need to do that again!)
I don't regret buying it, but I don't use it quite as much as I thought I would, either. I would probably replace the cutter if it got lost or stolen somehow, but I wouldn't bother to replace the straight-sided dies I've bought; I'd only replace the raggy & curved shape dies.