I tried the Digitech Drop with bass guitar. I wanted to use it with a 4 string bass with standard tuning in order to drop the pitch by a few semitones when needed.
The construction of the pedal is very good. Solid and reasonably heavy it gives you the impression of something that can withstand live usage without any damage.
The controls are intuitive and easy to operate. The only thing that I found not well thought out is the series of LEDs that indicate the setting. In theory, the idea is good. It gives the user a clear indication of the current shift amount and it looks great. In practice, the idea is not that good. If the stage is dark, one only sees a green light that roughly indicates if the setting is in the lower or high range. It is impossible to see if the setting is 5 or 6 for instance. If the stage is well lit, the LEDs are not necessary and another type of indicator would have worked equally well. It is not a major point though.
Sound-wise, at least with bass guitar, the Drop doesn't work that well. The tone of the note is solid but, for the lower notes, there is a fairly strong vibrato that tends to be less present with notes on the A string.
The Drop struggles to track effectively the lower notes. When the signal is strong, the tracking works well but when the note fades, the tracking gets confused. I can't hear any significant latency.
I was impressed but the last setting (octave down + dry). The sound was punchy and full. The presence of dry signal somehow mitigated some of the weaknesses of pedal.
Judging exclusively from the viewpoint of a bass player, the Drop is not something I can recommend. The octaver-like setting works well but other pedals can cover the same territory more effectively and with more flexibility. It is a shame because on paper the Drop had the characteristic to be a great pedal for bass players.