If you want to use the phone without the OpenVPN feature then it's a great phone easy to set up and get working. But if you want to use the phone with the OpenVPN feature then the documentation is a little rubbish.
With some better documentation on how the tar file needs to be structured and how the VPN needs to be set up then I could definitely recommended this phone.
It was thanks to this guide [http://www.sunstatetechnology.com/docs/YealinkOpenVPNGuide.- pdf] that I managed to discover the required layout for the tar file to get the phone to connect to the VPN.