(1) This should be an interesting race. The four term Democratic incumbent is retiring, so it's an open seat. Before the current mayor took office, the city was reliably Republican in the 1990s.
(2) Columbus is the largest city in Ohio, and Ohio is a key swing state in the Presidential elections. Columbus is also on the shortlist, and considered a leading contender, to host the 2016 Democratic National Convention.
(3) Columbus has a non-partisian primary system and runs on a slightly offset calendar to other US municipal elections. That means the primaries will occur in early May, the general election in early August. The two top vote getters from the primary will face off in the general election. This will give some early predictive power for the Fall of 2015 elections in the US in terms of which party is trending, but also be a more interesting race to follow during spring/summer of 2015.
The General Election is August 4th