Ranked choice voting (RCV, or “instant runoff voting”) was used for the first time in Portland, Maine to elect the mayor in November 2011. The city voted to use ranked choice voting in November 2010 at the same time they decided to have an elected rather than an appointed mayor position. The position of Mayor in Portland had not been elected for 88 years.
The high interest in the election made it very competitive, with 15 candidates running and voter turnout about 50% higher than election officials predicted. All evidence suggests voters adjusted well to the new ballot, and reactions to the use of RCV were overwhelmingly positive.
See FairVote's Ranked Choice Voting in Portland, Maine page for more information.