Well, it is not THAT bad that you should get rid of it. Just don't expect razor-sharp photos from it, especially when used with telephoto end of a zoom (basically, these converters are designed with the aim of "extending" the focal length of relatively "modest" primes such as "standard" 50mm, or 35mm, so that one does not have to buy a "portraiture", or, if one already owns a "portraiture" 100mm, he does not have to invest money in 200mm+ "strong telephoto" lens...). You could find yourself in a situation where you just WANT to take the photo that is soft or blurry, in order to accentuate certain "atmosphere" etc., and at the same time you need to "reach a bit farther", but all you got with you at the moment is that 18-55mm and a converter...