I went a couple of years ago and I didnt think it was too fantastic honestly. It might had had to do with the fact that it was 97 degrees out and the last thing you want to eat is hot soup- but all in all- I didnt think that the chowder on display was worth the crowds.
Just my opinion
Quality varies from year to year. Sometimes they have three or more really great chowder options and you can go back and forth until you can pick a winner.
Sometimes there is only one restaurant with good chowder. There's usually one place with really bad chowder - you see people dumping the cups in the trash after taking one taste.
The weather is a huge variable. If it's sweltering, it's not so much fun. If it's sunny and dry, it can be a blast.
Just watch out for all the corporate junk set up outside the Chowderfest - giveaways of junk food and chemical-laden drinks.
I went about 3:30 and there were zero lines, at most I had one person in front of me. I too liked Christopher's the best, it had that pronounced dill flavor, which might not be everybody's cup of tea. The Oceanaire's was interesting with the parmesean undertones and oddly I thought that Chicken Bone's was my second favorite. There was one wallpaper paste chowder I couldn't finish. Hall of famer Turner Fisheries' example didn't impress me that much.
I also think this event would be better held in Sept/ Oct. Every time I go it is a sweltering experience. I felt really bad for all of those poor folks dressed in the Blackberry (the phone) outfits.