Can't comment on Airtex directly other than there have been a couple of magazine features that included them and Light Plane Maint. talked about them last year (Oct 2001 Issue) when they did a feature on refurbishing aircraft interiors.
As I recall the article, they are one of the few sources for fully approved materials and LPM stressed the need for approved materials.
I went the Aerosheep route on the front seats (on which the leather was getting badly cracked and split) and the sheepskins are great, both in the summer and winter. That said, the summers in England are not that warm at the best of times, but on the warmest days they were still very comfortable - never sweaty. They are easy to install, fit pretty well and are very comfy over all.
Also significantly less expensive, circa $385 plus shipping for the pair and no down time - well, I think it took an hour total to install them including seat removal, relub and re-install and log entry. I post justified having bought the Garmin 295 with the money I was going to save on the interior by going the Aerosheep route.
Regards - Dave