This was my very first race in 2008 and I've done it at least 5 times since. It's a beautiful race - some years the blossoms are out, some years they've already peaked, but no matter what it's a beautiful course going all through downtown DC.
The only drawback of this race is that it is CROWDED. You will have to weave no matter what, unless you are starting with the elites. They do not enforce the corrals and there are people who will literally walk from the start, even if they are in a corral that is supposed to be 8 min miles. Parts of the course are incredibly narrow and it can be really difficult to find a spot where you can keep your pace.
The start/finish is beautiful, right by the Washington Monument, but it's not particularly convenient (close to a few metros that get very crowded).
At the finish, you have to walk quite a ways to get water, just a heads up. And the bananas (I mean, why do we do races?) are nowhere near the finish line.
In general, it's well organized, beautiful, and fun. But be prepared for major crowds and not the most amazing logistics in the race world.