I don't get it, it sounds like shit. What would you use it for? Did anybody ever use it in any track?

I just found out that on the boss 303 mfx11 is called LOWBOOST.

Is that the same as OCTAVE, which is the mfx11 on the 404.

it orks pretty well, but as any other octave efx you can only use it on one sound at time.. a melodi f.eks. but if that melody has a place where there is two or more notes at the same time it sounds shit.. great for making your guitar soung like a bass..

Use it on synth sounds. I used it all over "First Day in the City" and it sounds cool on the synths. It sounds crap on bass sounds though.

where can I hear that track?

In the Music section - in the thread called "Cartesia's synth sounds".

The effect is used on the lead synth after the breakdown - it really thickens the sound, much like chorus but not so dischordant (or cheesy!).