I really like it. I use it in addition to my vest sessions instead of as a replacement however.
In the past I've had problems with the magnet getting rusty on the inside of the device. I use it attached to a neb. If you are using it that way make sure to rinse the inside thoroughly after each use. The manufacturer told me they are working on this issue. So hopefully you will get a newer one that has this corrected.
Enjoy!
Steph