I assume you did basic troubleshooting. Same issue with a new user? Same issue with a fresh system booted from an external disk?
I have 2 Yosemite installations, 2 Mavericks, 1 Snow Leopard, 1 Mt. Lion.
The 2 installs are on different drives.
These issues are persistent in Yosemite only.
It's as if the more Mac OS X gets better, the worse it gets.
I could not recommend Yosemite to anyone if you're happy with Mavericks right now.
In other words, if there's not a feature you don't need or have to have, I'd wait.
It's just way too buggy comparatively.
And I'm running a Mac Pro with high end graphics, not some Mac that meets the bare minimum requirements.