Sequential Pro 3

Very big problems with the actual OS, crackles, pops and clicks from the effects section, no midi transport with Local Control OFF in Ableton, sequencer. Completely unusable in Ableton Live 10. When I switch a preset with a Program Change command from a DAW the Pro 3 goes nuts. The sequencer in Pro 3 starts blinking like a christmas tree on crack and some crazy noises comes from the instrument. Sometimes it just freezes up completely. This happens every time when a preset have the Pro 3 sequencer running notes or automation automatically. A lot of firmware issues also some people experienced hardware issues with the cutoff knob and pitch wheel, check the forum.sequential.com if you want more info.
Sorry but I don't recommend it, I'm returning mine this is my first and last Sequential.
Bad experience!

I was torn between either getting a Moog Sub37 or PRO3, but at the end of the day PRO3 now sits in the studio as one of the main synths.

The main thing i love about PRO3 is the tuned feedback module! Absolutely stunning and gnarly. And you can route external audio to it as well. So for weird and heavy bass sounds or even leads, it's perfect!
And for warm analog sounding stuff it pulls it off extremely well, for simple warm synth bass you can just have 1 saw osc , record some audio in the project while jamming with the filter cutoff (amazing filters btw) and then i use Fairfield Circuitry's Shallow water on top of it. You instantly get something warm and soulful.

Easy to use, not too much menu diving needed, can do simple stuff really well and you can go pretty crazy with the sound design stuff as well.

My only 2 cons are

1) I don't really find myself using the sequencer a lot (compared to Arturia minifreak's sequencer, which is hella fun)
2) The built in effects(reverb, delay etc) don't really impress me much. Compared to Novation Summit or even the Arturia Minifreak, which have amazing sounding fx, the PRO3 usually gets sampled to audio in dry, and the fx come from either DAW or pedal's afterwards.

But all in all, an amazing piece of gear to have in your everyday arsenal.

Love this synth, it delivers that Sequential sound for lower price.
Amazing arp and sequencer.

Only minus points that I have is the plastic on the sides which can give a cheap kind of look, but not a biggie.
And the paraphonic is not always working as expected. That's understandable considering the fact that it's a mono synth. But other than that it's a great synth for my studio.