I received the 6.01 watch software Thursday and am still running 5.11 on the S6.
Other than not having a dialer the watch can now place and receive calls. I used OK Google. When the watch rings, there will be a green partial circle peeking in from the left to answer, alternating with a red partial circle from the right to ignore and/or send watch greeting. Or let it go to voicemail. IF you answer by pulling in the green indicator from the left, you are presented with a special set of level adjustments allow adjustment of mike and speaker. Speaker should be all the way up if there is any noisy environment around. However it is adequate for driving if your hand is on the wheel. Microphone picks up well. Sounds like you are talking on the phone. The usual large blue mike and speaker icons are present during the call which route audio to/from the phone.
Dragging those two Icons to the left present you with the hang up icon which is a phone handset. Press to disconnect.
After receiving the update, go over all other watch settings. Ring tone, ring volume, etc are available in main settings along with gesture options. Call volumes are not. No changes were made to the phone.
Unknown if Wi Fi is necessary. I run mine all the time anyway. That's all I can think of, your mileage may vary. I called my son when I got it working and he stated he couldn't tell the difference.
It was worth the wait. Again, this was a watch software only update, phone is the same as it was prior. Now going to look for a good dialer.
Hope that helps
Ben