Pros
Fast and fun
Great for making beats and blips
Nice effects add character to your tracks
Cons
Slow sample loading
Not studio-quality: 32 kHz sample rate and tinny reverb
Need extra gear to control pitch if you play it as a bass or lead machine (or you could record your knob twists then step-edit the result to make sure everything is on pitch. Possible but a tedious.)
Loved mine and regretted selling it 12 years ago. But imho, the modern ES-1 is TriqTraq for iOS and Android. It’s smaller, deeper, cheaper, mobile and even more fun. If you’re into that sort of thing. 