I have been using the Freedom chair for 5 years now and it is by far my favorite chair. I tried the Aeron chair, which a lot of people swear by, but I couldn't get comfortable in it. What I will say about the Freedom chair is that if you are on the heavier side, it is not the best chair due to its lack of tilt lock.
Freedom chair and Aeron chair are from totally different companies...
I would get the stay away from their blue chair as it is more like a deep purple. You can't go wrong with black.