I had an ESQ-1 and used it mainly as a controller too great controller! I like it as a synth too once you wrap your head around how it functions it has a very soft mellow sound to it if you want to make some different kinds of sounds imo. There is a good plug in emulation of it too I forget where its at.Now, this must sound stupid..
I love to play on my Ensoiq ESQ-1 from 1986. It´s my main midi synth wich i use mostly as an midi only. The sound are quite cheesy, but i have had mine for over 15 years and i can come up with quite decent sounds..
Otherwise i must say the best synth of alltime are the Access Virus TI 2. There is a point where raw DSP power beats the analogue..