I love our CSA so much. It is way cheaper than the farmer's market, though not cheaper than buying conventionally grown vegetables in the grocery store. But if getting local, organic food is important to you I think CSAs are the way to go. Plus, everything we get was picked the day before and is notably fresher, sweeter, crisper, etc. Our friends comment on it when they come for dinner (and who ever compliments lettuce?).
Our CSA is year round, and some weeks we get so much produce that it's a battle for 2 adults to finish it all (especially in winter, when it is big bunches of leafy greens and root veggies). We eat a ton of vegetables. Generally, it's 8-10 items for $20, about 7-10 pounds. When it was just me I swapped every week with a friend. Our CSA has expanded my cooking repertoire immensely. Just a few weeks ago I was commenting to my husband that we routinely eat fruits and vegetables I'd never even heard of before a few years ago.
Eating seasonal has it's ups and downs. I like almost all vegetables, but there are moments when I think, how many radishes, turnips, and persimmons can one person eat? But, on the flip side, we get the best heirloom tomatoes all summer long. Nothing is as good as fresh peas and leeks and asparagus in the spring. The oranges, which we get all winter, are the best I've ever had, as are the peaches in the summer. The carrots are so sweet and crisp that they don't even need to be peeled, let alone cooked. So I say, if you can find a good one go for it!