I'd recommend the OC Marathon for any of my friends who may be thinking about running such a course in the future. (www.ocmarathon.com) It's a scenic course with easy rolling hills and, important: easy parking on either end of the course and well-managed.
I understand this was only their second event. And, when they did this last year for the first time, they pulled in about $300k -- almost unheard of for a first event, I understand. This year I understand they were expecting something on the order of about 25,000 runners and pulling in even more for charities and community events than what they pulled in last year. But, those reasons alone aren't why I recommend it.
The course starts at the Fashion Island Mall in Newport Beach where there's plenty of parking. The course then winds through picturesque areas of Newport Beach, then Irvine -- all the while getting to run in the middle of the street. (That's one of the main reasons I run it. Well, that and to get a new shirt.) Through Irvine, the course runs along the water canal and, at one time, by a lake in the Woodbridge community. (I know this b/c I have a real estate business.) ;-)
It's a well-managed event with water stations -- some with 'gu' -- at every 2-3 miles. (What's Gu?) And, the display they use for the race results is pretty up there with Star Trek. (Race results - Mel.) <-- Proof that I did run and finished the race. :-)

