Spring reverb is NOT like pristine digital reverb. Don't get it for that, but do get it. When added to the end of a patch, you can use it as a strange, otherworldly, organic reverb that leaves a metal taste in your mouth. But this is a modular synthesiser, so you're not confined to that. You can instead put it before the VCA, which stops it being reverb and starts it being a strange little creature that makes your patch sound more organic or real-world in a way that's hard to identify. It stops sounding like a synthesiser and starts sounding like a weird thing that might physically exist. In short, it introduces some complicated real-world physics into the mix.
So let's look at this particular spring reverb by Doepfer. The build quality isn't great, and it might benefit from a little re-soldering. If you're into modular synths, which are a pretty niche market, this probably won't be too difficult for you. It works just fine straight out of the box, but looks like you need to treat it carefully if you're not confident repairing it yourself later down the line.
Having said that, the features are great. The "emphasis" knob EQs the midrange, I believe, making it sound brighter if need be. As well as the regular inputs and outputs, there are extra ones for the feedback loop, so you can amplify the signal to lengthen the tail, filter it with any filter you already have, and so on. These simple features make it very open ended.
I also hear it's pretty easy to swap out the reverb tank -- the physical spring reverb in a metal case, that you plug into the main module -- for a different one, should you want to, for even more possibilities. Personally, though, I haven't found the need: this module is already providing me with so many things to try out, that I've still only begun to scratch the surface.
Spring reverb in general has a very distinctive sound, so check out some examples online before you decide whether this is for you. Personally, I'm making it a big part of the latest evolution of my signature sound.