I love mine. The value of the Korg should be equivalent to the ESQ1 though.
Alternatively, the VST SQ8L is very similar in sound, and free.
The main draw are the three oscillators and the amount of modulations as well as the multitimbrality. The analogue filter is the weak part of this synth making the all digital VST very easy to substitute in a pinch.
@6581punk: Just send an oscillator value out of the normal range, and the ESQ will read random bytes of code as wavetables. No mods necessary.