I have found that upgrading to Apple's router at home helped and then the latest patch of Yosemite helped a bit more so that now I find that my MacBook Air is performing well and dropping out largely gone both at home and at work. Sometimes initially it does drop and then is stable. My experience is that Yosemite wifi is less tolerant than Mavericks so that if the wifi network is strong, it is fine, where it is weak, old standards etc, it is more problematic than was the case with Mavericks. If you can get some tools to check your signal. The cheapest is holding down the alt key whilst clicking the wifi icon top right hand side of the screen. That reveals a lot of data about the connection - the long list greyed out. Look for the TX rate, transfer rate and the PHY Mode, If the TX rate is poor (say less than 50) and or the PHY is an old standard (say g); you have in my uninformed view a weak signal. If the TX mode is fast and the PHY is N or AC than you are getting a good signal. What I find is in my office the TX is 12-30 and it is just not good enough. Then I go places with 540 or even 860 and I get very fast downloads and stable connectivity. Hope that helps a bit. Good luck
