The worst bike shops that I've visited over the years are mostly closed now, due to being in a city with a cyclical boom and bust economy. (Very Darwinian) There was the shop owner who insisted that the bike with the 56 cm top tube and 12cm stem that I bought years ago was a textbook perfect fit for me. I wanted a shorter stem because I was getting a very sore neck on this "textbook" bike. I bought it elsewhere. This same guy tried to sell me a road bike that he insisted had Columbus SL tubing. It had no sticker and was suspiciously heavy.
There were all the shops where the clerks assumed I was a newbie simply because I was female. There was the mechanic who nearly ruined a track hub that I brought in for maintenance because I couldn't convince him that the lock ring was a left hand thread.
The shops where I live now are all okay. Not outstanding, but okay. The one where I found my new road bike wouldn't normally be my first choice, as last year I went looking for replacement Look Keo cleats and one of the clerks didn't even know what they were. However, they have one mechanic who is their road bike specialist, and he's great. Knows his stuff and never patronizes.