Variable scores on this one, but mainly for specific features rather than its sound
Interface - To be honest, I'm not entirely sure what the A, B, C, D knobs do - I think they are types of wave distortion - soft, hard clipping etc and maybe split into frequency bands. I'd like it to be clearer, but there are only a few knobs you basically just play until you've got the distortion you want by ear.
Presets - none. Id like some so that I could know what does what, but again, it's the kind of plug you just experiment with.
VFM - free
Stability - mostly excellent. It always works well until you turn on the oversampling - more often than not my system crashes when I use it - dunno why. But I'm happy enough without it.
Features - quite a big variation in the type of distortion you can get. It doesn't seem to do that lovely warm gentle overdrive, but will certainly scream with nasty distortion, and the subtle distortion is quite gentle (still identifiable as distortion rather than overdrive, but very musical). That's one of 2 main reasons why I like this one It can be a real screamer, but in moderation, it won't swamp your mix and it's useable - some distortions just stand out too much even on mild settings for my liking - Nastyshaper can do both easily. The other main reason is a follow on from the previous. I often use it on drum groups with almost no distortion and it works like an exciter. Subtle stereo distortion means you can add just a hint of crunch (like you could use limiting) to add the top sparkle, but it adds the stereo field, making it excellent for livening up tracks using mono drum samples. In fact I use Nastyshaper as an exciter more than as an out-and-out distortion effect. Not as extreme as something like Cyanide, but then you can't use Cyanide as an exciter. Also try it out on something like a 303 emulation - not all of those are that close to a 303, but you'll be pleasantly surprised what Nastyshaper does to basslines if you use it very subtly. Or any bass sound (doesn't have to be a 303) When you do get it screaming, using the 4 pre knobs can alter the tone alot, giving you a fuller bassier sound, or a harsh scraping toppy sound. I don't play guitar, but imagine it is very useful as a guitar pedal because of this feature.
So that's it.... there's only so much you can say about a distortion FX. I prefer Nastyshaper over commercial ones simply because it has other uses and doesn't overdo it at low levels. It's certainly not a valve type of distortion, but isn't meant to be so it achieves its aims well. And it's easy on the eye too. It's become one of my stidio essentials - not always used, but appreciated when it is - for being simple and musically useable - not too many bells and whistles to get in the way, which is what a studio essential should be.