heyaaa, this might have been done by others but i guess it won't hurt
so .. I just bought the EHX Holy Grail for half-price off a craigslist local deal, can't resist .. I give it a try.
basically it is a simply enough pedal that many guitarists and bassists swore by it. It has 1 REVERB level knob and 3-switches mode (Spring, Hall, Flerb)
when I engage and disengage the pedal, there's no hissing or noise whatsoever, exactly my liking .. quiet pedal.
what works for me, may not works out for you but for me, the max that I like is to set the REVERB level to 1 o'clock for any slapping lines and for finger-style pluck I can withstand 2-3 o'clock over that is a little too much as your bass punch is no longer there but just some reverby empty space out there in the galaxy somewhere ..
the 3 modes...
- Spring: the most subtle of the three modes, very noiseless and clean, very basic reverb signal delivered here, this is a very sweet setting love it and what many others like too, if you want just a 'fuller' sounding basslines that your usual playing then spring is your mode.
- Hall: similar to above but unlike Spring setting, Hall's much luscious, wetter, and much more SUSTAIN than Spring. I find if very awesome for some notes, sliding, chords and harmonic for this, but personally, I won't use it for a heavy rock punk lines as it would be very messy

Out of the 3, this is my favorite!!
- Flerb: flubber is flying rubber, so .. flerb is flanger-reverb, not too bad but I guess this work out greater on guitar than a bass, but it works fine as well on my bass and does not really lose any low end. This has similar sustain level with Hall setting but this has a flanger-y type wave that oscilliate as you hold down your note

not so sure where to use, but this does give you the wow sonic feeling to it.
Question: is it a good buy, come on .. at this price, I can't say no. But overall this is a very good reverb that work fine on bass, jump on it fellow bassists! I might go on to try other brands but for now, this is a keeper fo sho...
I am using my Jaguar bass, orange Bayou Cable into Holy Grail .. into

a 10W practice amp ..