A bit too early for me yet based on the recent iOS problems. I've also recently noticed that the last 10.9.5 upgrade to OSX seems to have stopped the scanning function on my HP AIO printer working correctly
HP printer I admit was my own concern, as yet no definitive answers on total compatibility that I can find.
HP printing still works fine for me in 10.9.5 I get the impression from a few internet searches that the scanning issue may not get resolved. As a work around I've started using 'Image Capture' which fortunately works fine and see's the printer on my wifi network. Whether or not I dare move to Yosemite I'm not too sure, I might call it a day now and stick where I am. I'm running a mid 2010 MBP and it does seem to get a little slower after each upgrade.
Upgraded yesterday. No problems during a normal day of use; basically internet, itunes and photoshop. Didn't try my printer yet. Edit: basically Omega Forums, internet, itunes and photoshop
HP software is notoriously crappy. Upgraded to 10.10 a few days ago, no issues so far. User interface looks much cleaner than 10.9. Seems good so far.
I quite like it, especially now with iOs 8.1 on my ip6. Texting green-numbers is nice as is calling with my macbook.
Spoke to soon re problems, one that is doing my head in, screensaver constantly reverts to National Geographic. Ok! some nice images but not a single watch amongst them
I've read quite a few reports today about wifi issues. Slow connection speeds, dropout and some total failures to even connect.