I have a version 1 ergohuman (black, mesh, headrest) see here
. I've had it for a few years now and I'm very happy with it.
When I was shopping for one I was looking for something mid-high end. I found that the aeron chairs are commonly held to be the best thing since sliced bread (in terms of chairs), but there are two issues (besides price) that put me off them and lead to going with the ergohuman. Firstly, no headrest; people have had to resort to building and custom fitting their own. Secondly I wasn't impressed with what I was hearing with regards to back support. There are two options, lumbar and "PostureFit"
, I think it's lumbar that comes standard, the other you have to pay more for. If I remember correctly, the lumbar support is essentially a big block of polystyrene and pretty easy to break; the other I think is supposed to be better, but obviously more costly, and I worried about how flimsy it kind of looked in pictures. To be fair though, I ordered based on pics on the net only, I didn't ever go and actually try any chairs in store.