Any of the FM transmitters are going to have drawbacks depending on the car you are in and where you are driving. They can get interference from other radio waves. What might work in one part of your city might not work in another part. Just like listening to regular radio.

I would put the transmitter you bought back up on eBay. You'll have to eat the difference between your cost and what you sell if for but it will be better than losing the whole $50. Then look into a hard-wired solution like mentioned above. I've found cheap and easy ways to wire an aux input for both my Miata and a Subaru with stock factory radios (of course I've been too lazy to do anything about it).