Yes, a clay-tempered katana can be considered good due to the benefits it offers. Clay tempering, also known as differential hardening, is a traditional technique used in Japanese sword-making to create a hardened edge and a softer, more flexible spine. Here are some reasons why a clay-tempered katana can be highly regarded:

1. Cutting Performance: The differential hardness achieved through clay tempering enhances the katana's cutting ability. The hardened edge retains sharpness and provides excellent cutting performance, allowing it to slice through targets effectively.
2. Strength and Resilience: The softer, more flexible spine of a clay-tempered katana enhances its strength and resilience. This allows the blade to absorb impacts and reduces the risk of breakage during use.
3. Aesthetics: Clay tempering creates a distinct hamon, the wavy line pattern along the blade, which is highly valued for its aesthetic appeal. The hamon adds to the visual beauty and uniqueness of the katana, making it an attractive feature for collectors and enthusiasts.
4. Craftsmanship and Tradition: Clay tempering requires the skill and artistry of an experienced swordsmith. The process is steeped in tradition and reflects the craftsmanship and expertise of Japanese sword-making. Owning a clay-tempered katana can be appreciated for its connection to this historical and cultural tradition.

However, it's important to note that the quality and performance of a katana depend on various factors, including the skill of the swordsmith, the quality of the steel, heat treatment, geometry, and overall construction. Clay tempering is just one aspect of the sword-making process, and other factors also contribute to the overall quality of the sword. It's always advisable to consider the reputation and expertise of the swordsmith or manufacturer when evaluating the quality of a clay-tempered katana.