personally, i think the idea is great - for an option that is acceptable to capitalism. (i have participated in a few csa's over the years, mostly as a "community supporter").
what ba@ describes (after the first year or so) is much more what i would seek out. but without the business aspect of it, it isn't really a csa (imo). and that is the primary critique i have:
it is still an economic arrangement, and a capitalist endeavor.
though, on the flip side, at least you know what you are eating.
growing food with some known and trusted folks, with NO economics involved, would be far preferable, to me. you may say i'm a dreamer...