I will miss Spinrock. It was a decent example of an Afterburner style ride which slotted nicely into the park's lineup. I'm quite surprised it's leaving as it still looked very fresh and well presented. There were no hints of age in the ride experience either.
Perhaps it's because I'm used to the Merlin approach of running a ride until it's on its last legs, barely able to limp its way through a cycle. Even so, there are many rides that I would have expected to go before Spinrock, not least that awful suspended dark ride.
From what I've read, I'm guessing that Zamperla Discoveries are significantly better than Huss Sledge Hammers. I've been on one and I was quite disappointed. It suffered from the same problems as AtmosFear in that it was far too bulky and cumbersome to provide a thrilling ride.