Kakashi, who was inexperienced with Kamui was able to "warp-away" an Asura Path Missile. Once you're targetted by Kamui, you cannot escape unless the Kamui Caster [Obito, Kakashi] stops it themselves. For example, Deidara detached an arm.. he couldn't stop the Kamui. Minato has been shown to be the only character able to successfully "exit" Kamui, which was through another S/T Jutsu, Hirashin. However, it is over-hyped.. Kakashi, in no realistic case-scenario will just use Kamui off the bat. It is not the greatest jutsu ever. In fact, I believe that Susano'o is a better Mangekyo Sharingan technique, but that just be me.