On OCT2 mode, I have the Level @ 3 o'clock, OCT1 @ 12 and OCT2 @ 8.
On POLY mode, Level is @ 3, OCT1 @ 9 and RANGE @ 5 (Full).
I never really use the DRIVE mode.
I didn't really bother to compare this to other octaves, I liked what I heard and the price so I went for it. Never tried the OC-2 or EH Octave Multiplexer or EBS Octabass but I am curious.
The OC-3 is not the fastest when it comes to tracking but I think it tracks well, happy with it so far. Everyone has different expectations so I don't know, for me I love the sound specially when you pluck hard and combine some clean tone with it - that's why I crank the direct level higher.
And also, what do you mean by it only works on certain parts of the neck... If you use the POLY mode and keep the RANGE low then it will not work on the higher notes of the G string - like 15th fret and above or so... So crank the RANGE so that it works on the widest spectrum as possible. This is in the manual.
And of course it's not gonna work too well - at least not to my liking - on the super low notes like on a B string... I think the octave effect in general shines in the higher registers, I personally don't need 1 or 2 octaves below F#.
My only real complaint is that it sucks a battery like it's part of the buffet menu.