There are hundreds of great software synthesizer VST out there, and you probably already have several - so why should you care about Phase Plant? I think Phase Plant by Kilohearts stands out from the crowd because of the way it seamlessly combines different types of synthesis, with so many effects, with such a great modulation system. If you think about Serum and why it became more popular than Massive over the years, it mainly had to do with the UI and its ease of use. I think Phase Plant does that same thing for the hybrid synthesizer market.
If you aren't familiar with hybrid synthesizers, basically it means that the instrument can do multiple types of synthesis - in this case analog modeling, wavetable synthesis, noise generation, FM synthesis and sampling. Most synths (including Serum) can do several types of synthesis, but the focus is often on one type. Phase Plant is more similar to something like Falcon by UVI in that its pretty agnostic towards with synthesis type is preferred.
Phase Plant is also indirectly a modular synthesizer. When you open the synth you get a blank screen that makes no sound, and you have to add sound sources, filters, effects, and change the routing of these elements. Don't worry, its all very easy to do by dragging and dropping these elements around, but it naturally puts you in the mindset of modular synthesis.
Just take a listen at how diverse you can get with the sounds in Phase Plant.
One interesting aspect of Phase Plant is that all of the audio effect plugins, or snapins, that you use in the synthesizer can be used separate from the synth inside your DAW. So your purchase is in effect twice as valuable since these audio effects are quite good. The pricing model of Phase Plant is kind of confusing, but basically they offer 4 different pricing models (one of which is subscription based if you prefer than buying upfront), and each option changes how many snapins you get with the synthesizer. All the presets will still take advantage of any snapins they were designed to use, but you won't be able to directly make new custom presets with those snapins or edit them if they aren't on a macro. Check out the detailed pricing and snapin list here: https://kilohearts.com/products/phase_plant
I've found Phase Plant to be very easy to figure out how to use, and I haven't had to consult a tutorial or the manual at all. It took me a little bit to figure out how to add modulations, but thats only because I didn't even notice the big modulation section at the bottom of the window at first - so that ones probably just on me. If you aren't familiar with modern software synthesizers you might need to look up a tutorial, but anyone thats familiar with Serum, Falcon, or Massive should feel at least somewhat at home. Phase Plant is deep and capable, but its not nearly as complex as something like Falcon to learn.
I'm having a blast with Phase Plant, and I highly recommend it if you need a new software synthesizer. If you have every other synth on the market you probably don't need it, but you'll definitely use it a lot if you get it.