Since OS X Yosemite's October 16 launch, MacRumors has been receiving a number of complaints from users who have been experiencing Wi-Fi issues

Extensive threads about Wi-Fi problems have surfaced on both the MacRumors forums and on Apple's own Support Communities as well, suggesting there are quite a few users who are seeing Wi-Fi connection issues after installing Yosemite. According to the complaints, Wi-Fi connections are sometimes extremely slow, resulting in long loading times, and in some cases, users are seeing their Wi-Fi connections disconnect continually after just a few minutes of being connected. Since upgrading to Yosemite, my previously-stable (with Mavericks) wifi connection keeps dropping. I have to click the wifi icon and re-select my network every minute or two.

  Some OS X Yosemite Users Plagued With Wi-Fi Connection Issues