I've been using the original Neoair for about 4 years now with no problems. The current equivalent would be the Xlite.
Temperature limit would be somewhere in the 0 to 5 degrees area (for me).
Rumour would have it that the crossways baffles mean that you are more likely to find an arm or leg falling off the side of the mat than with the longways tubes of the Downmat. I believe this.
This is the 3/4 length (short) original Neoair. A full length Xtherm would be the same length but about 50% greater diameter.