i've had one of these for a couple of years. it's pretty tough to get anything truly musical out of it sometimes, but it's fun to use.
korg is coming out with a new product that is sort of similar called the "monotron". it's got a ribbon controller, so you still slide your finger left and right to change the pitch, but there's no Y axis. i don't know how many people on this forum will understand what i'm saying but the monotron is a fully brown townogue synthesizer with the VCF from the classic Korg MS-20 synthesizer. so unlike the kaossilator you can actually tweak the sound.
