I couldn't wait for the update any longer and I moved back to Mavericks.
I didn't have any WiFi issues, but the interface lagged (even with transparency off), and in general all tasks were slower. Additionally, Airplay was randomly dropping connection and it had compatibility issues with a few important for me apps. I don't even want to mention Spotlight...
It's sad for me to say (after 8 years of using Macs), but Yosemite is a new Windows where only a restart (at least once per day) improve things for a while
.