It's a 3x oscillator, 100% analogue synth, for less than 150 euros. We can stop right there - it's a must have.
Plus it has a really cool sequencer, which is very intuitive and easy to use. Although limited to 16 steps (or one bar). However, you can connect it to your DAW via midi cable, have your sequences running from there, and have as many bars as you want.
Oscillators sound really nice, as well as the filter, which turns into a beast with a lot of resonance. Without running it through any external devices, you can get an overdrive, which is a nice little bonus.
It is marketed as a monophonic bass synth, but it's a lot more. Actually it has a secret. It's not completely monophonic. You can sequence different notes for every OSC if you're using it's sequencer, or set different semitones for every OSC. By these methods you can even get triad chords out of it, which could be useful if you're making dub / techno dub music for example.
Another great thing is that it has an LFO which can go very fast, you can enter the audible range with it. It allows you to get all kinds of weird sounds.
The only complaint would be, that it's build doesn't feel very solid, it's plastic, wobbly, feels cheap. But hey, for this price, it's OK. If you take good care of your equipment, it shouldn't be a problem. And despite all of that, it looks very good.
There's also a little speaker integrated, and it can run with batteries. But I personally, find these features useless.
Overall, excellent product. Definitely a must have if your budget is limited, but you want a proper analogue synth. And Korg Volca Bass is exactly that.