For the short cast-time probably. My 70 mage friend still has his rank 1 frostbolt hotkeyed. Yup. Its a shorter cast time then higher ranks. Out of interest, because so many people still use rank 1, would you bother training to get rank 2, 3, 4 etc? Well yes. The higher ranks are still needed for damage. The reason I have a rank 1 frostbolt is for when I need a quick slow without damage (like if I'm a fire spec). Part of my kiting might include using a rank 1 frostbolt because of the faster cast.