Apple have provided developers with the first Yosemite update for Mac OS X, asking to focus on three major aspects: Wi-Fi, the Mail application accounts Exchange, and the Notification Center. These instructions are reported to be mentioned in the brief release notes for the beta-build update.
The Wi-Fi connectivity has been problematic for many users, as it can be seen from the Apple's official support forum which is full of the threads claiming that Yosemite killed the connection. The issue has been up for about a month already, beginning from October 16. Yet, as this was mentioned to developers, it can be a sign that Apple have finally recognized that the update might contain some bugs causing the problem for numerous OS users.
A lot of unofficial fixes and workarounds can be found there too, but many of them ask for system configuration changes and are not a universal solution.
As the request has been sent by Apple to the testers, we can hope that the fix for the Wi-Fi connectivity problem will eventually appear and it won't take too long to wait for it.