It's a great time.
One of my favorite parts of the whole thing is the pre-events. The local homebrew clubs organize some events on Wednesday. One year (in Cincinatti), they offered a bourbon distillery tour in Kentucky, and a fun pub crawl. In Minneapolis we had brewery tours, a pub crawl, a Twins game, etc.
Thursday night is Pro Brewer's night, and some of the country's best breweries bring special things. Friday night is club night- and that's a great time. Saturday night is the banquet (not my favorite thing- food is ok, but the winners of the homebrew comp are announced) and there are wonderful seminars all three days. You can rub elbows with John Palmer and Charlie Papazian, as well as some very cool homebrewers from all over as well as learn from the experts.
I don't think I can make San Diego this time (friends are working on it with me!) but believe me, if you can make it- go! My husband won't go, as he likes beer but not in such quantity. Take a look at some of our pictures of previous NHCs. I have some in my gallery, and I know SoperBrew posted a bunch.