I have run several races in SF and this one is by far the biggest. However, it was well organized and even with a lot of people, the course opens up quickly at the embarcadero and it is easy to pass slower runners. The expo was pretty crowded and I did not really enjoy hanging out there, but it was well laid out easy to pick up your bib/shirt/etc and get out. The course is beautiful, but very hilly so don't plan on a PR, and there is sufficient water and gatorade throughout the course. I haven't run the full marathon, but I have heard the second half is not a good as the first in terms of location/scenery/cheering. I would do it again, but it is also really expensive and difficult to get into. The tiffany finisher medal/necklace makes it worth it :)