I have been following this forum for about 6 months now. It appears that people have different symptoms and some have discovered fixes, although temporary and often different. I "bumped-into" one suggested fix and I tried it. It seems to work ... partially.
Before, my MacPro and MacBook would lose Internet connectivity about every other day. To regain it, the computers needed to be restarted. I read a thread about turning off Bluetooth to avoid a potential conflict with the 2.4GHz channel. EUREKA ! It worked ... partially. I had to store my Bluetooth Mighty Mouse and and substitute it a wired USB version, but that was OK.
RESULTS: Good News and OK news. For a whole month now, my MacPro has not lost connectivity. As for my MacBook, I still lose connectivy, but much less often. Sometimes the MacBook will give me the "You are not connected to the Internet" message, but after 5-10 seconds it will establish the link. A few times, I find that I have to turn the WiFi off and then on. This always re-establishes the connection and restarting is not longer required.
So for now, I can livew with these minor inconveniences until Apple releases a fix.