This is a great experience in advance of the main event. It is open to anyone who wants to enter, not just the marathon entrants, and is a lovely route around the city, taking in the sky scrapers and getting the benefit of the atmosphere.
It's easy to find the start of the race, but not so easy to get into the centre of the city with all the people congregating to take part and spectate, so definitely make sure you leave your hotel in plenty of time (we ended up abandoning our taxi and rushing to the start!)
At the finish you get a decent medal and plenty of food and drink, and we were given fantastic bobble hats this year. Definitely do this race if you get the opportunity.