I wanted to make my guitar sound like a bass for a one man army setup. This is the third octave pedal I'm buying in the space of a few months: the first one had serious tracking problems, while the second one did not let me remove the dry signal, so no cigar.
The M288 has made my day. It tracks single notes perfectly - all the way from low E to the 17th fret on the G string. (It could be doing OK further up the scale, too - I simply haven't tried it that high.) It works equally well with all possible combinations of the two pickups on my old replica telecaster.
The M288 generates two bass sounds, Growl and Girth, both one octave below the input signal, but with different colouring. Girth is deeper, Growl sounds more aggressive and with more presence. The end result is a combination of each of these plus the dry signal. In my case, the dry signal is down to zero. True to its analog nature, the M288 lets you roll the Growl and Girth knobs (as well as the Dry knob) until you extract the exact mix that defines your sound.
And there's more. A mid frequency boost is available from a tiny button on the top left. It isn't very gig friendly - you can switch it on and off with your foot but you risk catching the Growl or Dry knob, so beware. If you manage to engage it, though, it is a great feature, allowing you to cut through the mix if and when necessary without changing your overall sound.
And if this isn't enough, the mid boost frequency can be reconfigured. They've hidden the dial in the battery compartment, so you practically need to dismantle the thing, but on the other side, who needs lots and lots of knobs and buttons out front.
Overall, highly recommended for guitarists who want to play bass without changing the instrument.