You truly haven’t experienced a tack sharp image until you have shot with a prime lens, especially for the price. The way zoom lenses have to be made (more moving parts) causes them to have more variations or possibility for variations.
Prime lenses, on the other hand, are set at a certain focal length (no moving parts besides the focus ring) and have the luxury of being able to offer a wider aperture. As a result of having a bigger aperture, the blessings are twofold. Firstly, you are able to capture more light without sacrificing shutter speed, and secondly, a wide aperture means more depth of field for isolating your subject from the background.
People sometimes forget that good equipment doesn’t directly lead to good photos. Of course, the better the equipment, usually the easier it is to get good photos – but sometimes that is not the case. Understanding how and why your equipment works the way it does is by far more important.
