I Have one (in fact 'gurulounger' sold it too me to replace my cz5000 many moons ago.
For a digital s+s synth it can create some wickedly FATTT sounds ,I mean dont pay too much for it but there is a PC editor floating around and it make editing an easy trick it also has a librarian as well so you can save all your patches via midi .One word of warning!!!! My ESQ1 has been updated to ver 3.5 which basically means it has a slightly bigger sequencer memory ..but after a few years gigging it can be a bit unstable live so now it stays at home also because it sits on a stand midied up to my PC the contacts under the keys are filthy (probably) and some keys dont quite work ,allthough this is not too much of a problem since they all ply through midi .....and if I could be bothered I'm sure i Could make them go again ....But it has some awsome sounds in it and you can assign the cutoff to the mod wheel (it has a wheel not a joystck) yeah ....if the price it right (and it should be ....no one seems to know how cool they are ) BUY IT as long as its not too trashed ...cause the likely hood of getting any spare bits is a bit remote.
Also it must be one of the first multitimbral (8 Part) synths that i can think of ...which can come in handy for some exta voices
Can you tell I like mine and I'd never sell it ???