I too have been working on Aeron chairs for the last 10+ years and have never found a better chair. I may not have researched as thoroughly as many others here but I too have back problems and they never show up on the Aeron.
As to the hard front hard front lip, that to me sounds like either poor adjustment or wrong chair size. There are 3 sizes to pick from and offices often don't contain all 3 to fit the worker's size. So, you may end up sitting in a larger chair than appropriate.
As to the hard front hard front lip, that to me sounds like either poor adjustment or wrong chair size. There are 3 sizes to pick from and offices often don't contain all 3 to fit the worker's size. So, you may end up sitting in a larger chair than appropriate.