In my opinion, they provided a good value, especially if you compare the CSA to shopping at a premium grocery store like Plumb Market. I was also very happy with the variety. As with all CSAs, you will need to learn to love leafy greens (kale, chard, etc), but you will also get a great supply of squash, potatoes, tomatoes, peppers, etc. I particularly love how a CSA forces me to be creative with my cooking.
A friend of mine is also in their CSA. Now that its winter and the CSA is on hiatus, every time we cook something its always obvious that the meal is missing something. I know a lot of people who have bought shares in other CSA's and they're usually disappointed with the monotonous amounts of cabbage and radishes, as thought that was all that you could ever grow in Michigan. Green Thing's CSA seemed to have a far better variety.
Both Nate and Jill are extremely knowledgable about all of the food they are growing, and about Washtenaw county. I highly recommend supporting them in their startup year!