They are also nice for bass guitar , and can be good for piano. I prefer them to U-87 on vocals. However I must say here that I've never liked the U-87 as a vocal mic in 34 years of using them. I found the U-47 could give sibillance problems on female voices, especially when used as a voiceover mic.
I wish I still had my U-47 - a rapper stole it from my studio shortly after I had the capsule reskinned! Doh! They are now ( 2009) seriously escalating in price, and in the UK 2.5k GBP might be average for a used one. Neumann have not made the U-47 fet for some years now.