I have an M3
Prefer it in comparison to the Siemens S450IP phones.
It's crashed and died in me a couple of times... As have the Siemens.
The main thing I don’t like is that call waiting cannot be turned off at
the handset / phones settings
Compared to Snom desk phones, it does not have half of the features.
It works though, good call quality, and much more speedy when trying to
do call transfers etc... Which are a nightmare on the Siemens.