Just Got one of these on sale for $20, here's my assessment:

Pros:
Build Quality is a little better than most comparable chinese pedals (i.e joyo, caline) I'd say it's on par with a modern EHX or MXR pedal, all pots, swtiches, and jacks are solid metal, while the Board is loaded with SMD components.
It came installed with a new 9 volt battery.
Easy to use (simple controls), & sounds nice & quiet (not noisy)

Cons:
Like many delay pedals called analog, it is NOT truly analog. It's heart is a digital chip (specifically a CD2399) built within an analog circuit, to make the delays sound "analog like." Not that this is bad, or sounds bad, but I wish manufacturers would be honest about this.
While it does not nice, its very subtle overall. It will not self oscillate (so no crazy spaceship sounds out of this thing) and has a pretty short max delay time (the stated spec of 350ms seems accurate to me).

Overall I think its fair for the $20 sale price, but not worth it at the regular price, since there are tons of cheap chinese "analog" delay pedals all over amazon for right around the same price that have a longer delay time & will self oscillate. If you're looking for a true analog delay, the cheapest one is the Behringer VD400, which, while plastic, blows this thing out of the water.

It was out of stock, so I never had a chance to purchase it and try it.

Very playable great looks don't like huge head stock

Great, quiet, analog, true bypass pedal.

Great purchase ...I have bought several items from Monoprice and very happy with every aspect and I will purchase again

I am pleased with the Indio AD-4 pedal! The only reason I gave 4 stars is because I have a competitor's delay pedal that gives a longer max delay. Otherwise, this pedal is great for the money!!

GOOD: cheap and works well enough for basic delay. I use it for acoustic and electric. This isn't anywhere as good as a $150+ pedal, but for for less than $30 bucks, it's a great deal. I'd bet it's as much as 99% of all guitar players will actually need. Pretty quiet as well. Unexpected plus, it really makes guitars sound more clear and bright. I typically play down a full step down, and that can sound muddy occasionally, but this really improves the sound by making the guitar sound more alive. But not as grossly bright/plinky sounding as a Taylor. Helps my McPhersons have a little more top end without that cheap Taylor-like sound while preserving the amazing mids and low end. Would be helpful for any premium Martin to eliminate that typical muddiness. On Lowdens or Santa Cruz guitars it will give them a needed little boost in gain, without too much noise. A decent tool for a stripped down show.
BAD: will literally eat a new 9V battery in about 15 minutes, so for stage work, a 9v supply is mandatory. No case is included, which doesn't make sense for stage use ... a simple, small zip-up padded case should be included even if they have to raise the price by a couple of bucks. For me, that's a big deal ... if you're only playing at home, well, then it's not ...

Good quality, excellent sound

This works well and helps me add just a little bit of delay to my guitar signal. Nothing to complain about, especially since it's reasonably priced.

Stopped working after using twice.