Specifically regarding temperature, I don't think Celsius is granular enough, unless you like working with fractions. For instance, in my home, I can feel the difference between 72 F (22.2 C) and 73 F (22.8 C), and I prefer 73 F. Fractions would be just as easy for me to decipher, but there are some dim folks out there that have to be catered to, because they are legitimate consumers.

Regarding other measurements, I agree that metric should be used, because it just makes sense. Millimeters are about as granular as 1/16 inches, so that would eliminate the need to work with fractions in most cases.