I recently got a mac mini that shipped with Yosemite.
It has the nice feature of completely killing the WiFi interface when you attach a USB hub - googling around it seems a Yosemite bug. I have been told that also using bluetooth devices (such as the apple mouse) can trigger the same behaviour.
So I'd say I'm sorry that the mac shipped with Yosemite, except that at least I received the fix for the privilege escalation bug.
It isn't just Yosemite... I had exactly this behavior with Mavericks on a new MacBook last year. Fired up a Bluetooth mouse, and next time I opened the lid wireless had completely gone.
I've managed to get it working after a fashion, although not reliably, and have come to the conclusion that Apple just don't do wireless well.
I had this bug plaguing me for a while. My WiFi connection would drop every fifteen minutes or so, requiring me to turn off the WiFi and then turn it on again. I was able to fix it by doing a clean install of Yosemite (from a bootable drive).
