I've gone through several machines for travel and have had great success with the Puritan Bennett - GoodKnight 420E. I haven't been able to spot forums on these different machines yet, but would like to understand the differences. I had a problem with my sleep doctor adjusting this machine for me as I bought it online. I offered to pay of course, but they refused. Said I had no prescription for an Auto Machine. So they took my auto PAP and set it on Ramp. I asked that they change it back and they wouldn't. I finally got it adjusted and the machine is absolutely great, adjusting to the pressure needed at night. Mostly it is an incredibly quiet machine. Now if I could just get a machine I could use on a plane so that the other passengers can rest.