I subscribed to Buff Rock last summer and it's true, there were weeks with next to nothing and others that were abundant, due to bad weather in the growing season. I planned to sign up again this year.
Even though some crops were scant, the grower threw in things like a bonus bag of apples and jug of cider. Nice touch.
I liked the delivery to my door rather than going to pick stuff up from the Angel group or having to actually go to the farm for the Grayslake one.
However - the farmer in charge of Buff Rock Farm suffered a fatal heart attack this past January. His widow sent letters to past subscribers explaining that she's exploring options for keeping the land farmed in the CSA method her husband adhered to - so far I have not had any further info from her about plans for this year.
Upshot is - if organic produce is important to you, you will be able to use it all up or share it, and the price (it's more expensive than the farmers markets) is not an issue, go for it. You're helping a small scale businessman and getting excellent produce.
Expect LOTS of greens the first few weeks!!!
Good luck and keep posting about the CSAs.
By the way, I see that WYCC Channel 20 will be showing a new program this spring called Chef's Afield about chefs and their relationships with the growers of the food they use in their cooking-many CSAs will be featured along with cattle growers, dairy farms, and other food procuders. Should be a good show.