It depends on what type you are talking about. It you are refering to the big, black
boom mics like Madonna and Britney Spears used several years ago, I couldn't agree more. They are fairly cheap and most do have a good sound, but they take away from the show.
The newer style, like the countryman and AKG are a different story. If worn properly, they sound GREAT! If the color of the mic matches the skin (or makeup) tone, they can not be seen past the few first rows. The sound is so much better than the typical lavs, it far outweighes the downsides of it (cost and appearance for the first couple of rows). These things do cost a pretty penny. I was doing lights for a high school musical (Beauty and the beast) and Belle couldn't be heard at all with the cheap lav mics they had. lI went with her to the shop in town that sells them, and we got the one that fit the best and worked for her several costume changes. We ended up with the AKG. She sounded great, and I paid about $300 for it. I had only stocked countryman before that, but I really like the AKG.