The first technique, Ipponnme, is the most important technique in any style of Iaido. Whether you are a beginner going for your very first grading examination or a master performing a demonstration (演武), ipponme is always done.
At my dojo, ipponme is always the first technique, to begin with, and last technique to end with. This is true for everyone no matter how senior one may be.  Some Iaido masters even think no student is worthy of a passing grade if ipponme is not done well. This should give you an idea of how important it is to get it down correctly EVERYTIME.