It works great, no issues there. It's the only portable machine I've found that delivers 2 liters per minute (lpm) and it does that with ease. It's terrifically well-built and is easy to use.

First downside is that it is HEAVY. It's probably twice the weight of most portable machines out there, so if you need this for walking around, make sure you can handle the weight and consider some sort of backpack that keeps the vents open.

Second downside is that it is LOUD. You are not going to use this in a crowded movie theater because it sounds like a lawn tractor while running. It's quieter at lower rates, but at 2 lpm it's obnoxiously loud. Pulse mode works great but it gets louder on inhales which I find obnoxious.

From what I've read since buying it, both the weight and the noise level are directly tied to the fact that it can produce 2 lpm, and given current technology this is just a limitation that you have to live with for this amount of capacity in a portable form factor.

Finally, it gets hot, so make sure the vents are clear at all time, and since the vents are on the bottom and only go up about 1/2 on the sides, beware of putting it down on a '70s shag rug. :)

Bottom line: it's heavy and loud and the exhaust vents get hot. If you can live with that, it is a supurb machine that produces a nice cool steady 2 lpm of very pure oxygen. Oh, and in the setup menues it will report exactly what the flow is and how pure the 02 is, which I find to be pretty great.

One last point - this has a "phone home" feature where it reports your use to your doctor. So far as I'm aware there is no way to turn this off, but you can put it in airplane mode after which it will revert back to doing this automatically. I bought mine outright so it's not calling anywhere, but if that's a feature you want this is a good choice.