I tried Bull Run and Farmstead at Charlotte Hall last year (I committed to Bull Run early and then hedged when I heard bad things about them).
Bull Run was a poor experience. Leigh, the owner, doesn't bag or wash his vegetables. Nor does he shade his picked veggies and they all bake in the late afternoon sun. This causes a lot of wilting in the summer and makes his greens largely inedible. He also tends to put off harvesting until his fruit and root veggies get really big, so you end up with woody eggplants and baseball bat zucchini. Other times, they're laughably inadequate, like the week when he offered 4 radishes per share. It's a shame that Leigh's veggies suck so much (and it's always one excuse after another for why his veggies suck, even though my other CSA and the local farmer's market had a great year) because he offers a convenient egg share and a nice fruit share. Leigh also grows a huge amount of pretty nice basil, so I was able to freeze a lot pesto last year. Overall, I'd advise everyone to stay away from Bull Run, it's the sort of CSA that turns people off of the CSA concept.
Farmstead at Charlotte Hall was much better. They bagged and washed everything and I got a good mix every week. They manage their shares really well, I never got eggplants or summer squash twice in a row. Even for high summer tomatoes, they try to mix it up by offering grape tomatoes one week, beeksteaks the next, 6-ozers the week after. Everything I got was in pristine, farmer's market condition, picked right at the peak. I always got enough of a variety to make a dish or two. My only possible complaint about this CSA is that their selection is a bit too safe. The tomatoes seem to be well grown commercial hybrids (though pretty tasty) rather than heirlooms. Not too many herbs. No surprise veggies (say a bunch of dandelions greens or parsley roots). Overall, I liked what I got from Farmstead at Charlotte Hall. The farmer's markets around here are so expensive that their CSA was a relatively decent value (though it was pretty expensive at around $25 a week).