Installed the new 3Cx Phone 3.0 on the Samsung Rugby Pro...and so far so good. All of the basics seem to function properly. Have not yet had a chance yet to see if the connection is maintained over a long period. Have only used on Wifi, will try over LTE this next week. Love the fact that there is now a Voicemail indicator.
The only suggestion I have, would be to change the "Out-of-office" Icon from one that looks like a house (home), to that of a walking person, similar to what you would see on a Walk sign at an intersection. If someone is using the PBX in a home office situation, it could be confusing.
Update...over LTE seems to be working just great.