I have an azn knockoff I got for twenty bucks off ebay. It's okay but noticably worse than a CD (imo). Would reccomend you borrow one from a friend to try before you buy.
i had a good one, and it was absolute rubbish. nowhere near cd sound quality and the reception was all fuzzy unless you kept it shoved up your cunt. try and invest in a head unit with an aux input.
I have a Belkin one and the quality isn't too bad as long as you pick a station that has free bandwidth either side of it so there's no interference. I'd say the quality is no better than a CD though, even with a good Belkin one.