No matter what chair you're in, if you are going to be sitting all day - get everything out of your back pockets! Otherwise you're putting strain on your lower back, and it might punish you someday.

I bought an Aeron over ten years ago and have never regretted it. Everyone's different, so go try chairs and make sure you have a return period. What feels fine after five minutes in the store may not feel so good after five hours of coding.