We had a DeVilbiss Pulmo Aide 5650D as well, which I loved; however, every 2 years something would go wrong with it and their policy is that you have to go thru a durable medical equipment provider (medical accessories store) and the local place would give me grief every time. Tell me they didn't carry that model, would take 3 weeks for the local DME to send the machine in and get one sent back. The last time they called after 3 weeks and said it wasn't covered under warranty, but when I picked it up I noticed the date on the back indicating the machine wasn't even 3 years old and there was a 5 year warranty on it. They hadn't even bothered sending it in!
At least with the pari, I call, they ship a new one out and send a mailing label for the old one. The 50 psi Mobilaire is a nice workhorse, but it's tough to find replacement filters and the start up cost is about $240-300 so sometimes insurance isn't willing to pay. The Devilbiss I bought out of pocket as a spare and it was less than $100.