What Type of Chair Do You Have?

I've been doing some research, looking for the most ergonomic set up for my body. I just purchased a new desk, an awesome Humanscale keyboard tray (I'll review this one soon), and a new mouse. But the most challenging task for me has been finding a good chair.

I've narrowed my search down to three chairs (so far):

• Lifeform Ultimate Mid-Back Executive Chair
• Humanscale's Feedom Task Chair
• Herman Miller's Mirra Chairs

I've sat on all of them for at least an hour while I talked to the sales person. This gave me some time to figure out what what I liked about each one, but the reality is the final decision may be influenced by price, since each chair costs between $800-$1500. 

Today I came across this fun chair over at Sci-Fi Tech called the BalanceBall, and the price alone sounds good to me. I've seen people sitting on those bouncy balance balls at the office, and this chair appears to have eliminated the fear of rolling your way to the floor by placing it inside a frame with back support and wheels. It may not be in the same league as the ones I mentioned above, but it was designed by a Doctor to improve posture and strengthen core muscles, plus it looks like a lot of fun. At  $80 per chair I think I'd be willing to try it out.

I have yet to make a final decision, so let help me out here. Let me know if you have any chair suggestions. What chair do you have? Do you like it?