I must be the only person who hasn't had any WiFi issues with any Yosemite builds.
Then again, I'm using a Time Capsule, which you would expect to be tested more.
If it affected everybody at once, it'd be fixed a long time ago.
I have zero Wi-Fi issues on my iMac but not on my rMBP which is horrible. My Air has some issues but not all of them. That's why Apple can't fix it but I'd really wish they just stop everything else and focus on Wi-Fi only.