Even though some of the negative reviews here could be legitimate, I suspect many of them are related to user error or misunderstanding rather than a problem with the product. I installed this relatively easily and it has a great sound with no problems so far.
For starters, make sure to note the exact product you are getting. There are 3 versions, one with just a 3.5 mm jack (what I ordered), one also with a USB charging port, and one also with a lightning port. On the product (and on Amazon) it says that you can't both charge and play music at the same time (this is probably why some people had sound issues). But if you install and use it properly it should work great.
Two other points to note: 1) if you have a case on your phone or device, you probably want to get a slim adapter so you don't have to remove the case. The 3.5 mm jack on this product is not slim and won't fit past most cases. I ordered this adapter (https://www.amazon.com/gp/product/B074S15X7W/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) and the sound is still great.
2) The install does take a bit of work as you have to remove some of the dashboard to get behind the radio (check out any number of YouTube videos on how). If you have a rear entertainment system that is already plugged into the white port behind your radio (we didn't), you'll also need a Y-splitter cable so you don't lose use of that.
Overall, this was a cheap way to adapt our older vehicle to stream music from my phone into the car.

This is a nice product. Easy to install and works nicely. I installed it on my 2009 Honda Odyssey Turing van. I am giving it only 4 stars because the sound output is not that great, the base doesn't come out at all. If you are not looking for that thump then you will not miss
anything. Also sometime after you remove the USB and replug it the system doesn't detect it.

8/1 update: Updated to 5 star from 4 star. As I said its easy to install. Initially my USB didn't work or worked sometimes but after I reformatted my USB to FAT file format I didn't have any issues. So make sure before using ur USB on the system it is FAT format. My USB was exFAT initially and thats why it was working weirdly. Now as FAT format it works great. Sound volume is good, I don't get as much base as I would have liked but for 40 USD thats all you can expect.

Good packaging and quality.

Installed in 10 minutes on my Odyssey. Works perfectly! Pure and clean sound. No issues with sound or noise.

Some hints:
- you can name your folders on your USB stick whatever you want (no need to keep structure, like CD1, CD2 etc).
- if you want switch folders - use "disk +"/"disk-" buttons on your radio.
- if you delete some songs or folders - remove it from Trash as well!!!!!! if not, player will play them too. I was confused for the first time. =)
- format USB sticks in FAT (other formats won't play)
- install it with Y-cable (if you want to use CD-changer as well)

Installed it in my 2007 Honda Pilot with 6 CD changer, XM radio, DVD player. The discription states that I had to disconnect XM for the proper connection to work. No problem, I'd rather listen to my personal music, but once I restarted the car, the DVD player overrides everything. So in order for my DVD/Aux to work or even my XM button to listen to the Aux port, I have to disconnect my DVD player also. That's 2 sacrifices instead of one. Price is right just not the income.

This product is pretty much worthless. Yes, if you get it installed then you can technically play music in your car from your phone/SD card/iPod/whatever but the sound quality is so bad that you won't want to anymore. For one thing, volume is cut in half. If you like your music at anything above speaking volume, I suggest finding some other product. The adapter also has the infamous "alternator whine" that apparently a lot of similar products have, which is annoying but eventually you can kind of subconsciously ignore it. The third major problem is the fact that the actual connection being made between the aux cord and my phone is horrible. Most of the time I have to fiddle with it for 5-10 minutes before I can get everything in a position where there isn't constant crackling, only occasional pops.

All in all, if you're looking for a way to install an aux port, find something other than this adapter. It's a horrible product that will make you start to hate all of your favorite songs.