Seriously, Apple is giving you something for free, and you're complaining that other people's products might not still work. You choose to go through this upgrade process. If you don't want to, then don't. If other people's products fail to keep pace with new versions of the OS that you choose to install anyway, then complain to them.
Compatibility is a valid concern (for me too, by the way), but blaming Apple doesn't make sense when this is completely optional.
Here here!
No-one is forcing people to download Yosemite Public Betas or Developer Previews. Developers are downloading DPs to ensure their products will work (via minor and major updates) when Yosemite is released.
People are downloading Yosemite PBs to either experience the bleeding edge and/or to help Apple nail down bugs...