I cast from my Android phone and tablet all the time. It's not jittery at all when the app has chromecast support. I can even play movies I have saved on my Google Drive, you just have to cast your entire screen (mirroring) and then play the movie. That does tend to have a reduction of quality sometimes.
I've cast a few things from my chrome browser on a pc, and it usually depends on where/what you're streaming. I streamed the Howard Stern Birthday Party and it had barely any loss in quality, but then I tried to cast a hockey game one time from some questionable website and it was pretty much unwatchable.
I'm using a new Asus ac router that's pretty much the tits though...