I can also report that FaceTime is working for me (10.10.2). iMessage was a bust as it just keeps giving me the "network error" message. When I upgraded my Mavericks to Yosemite (I did not do a clean install) I tried Messages and that didn't work as others have mentioned, but I never tried FaceTime as I thought that was broken too under Chameleon/Chimera. I had also set up 2 step verification before I upgraded to Yosemite. When I tried FaceTime after the upgrade I got a message saying that I needed to set up an app specific password due to the 2 step verification. I went to the Apple ID site and set up the password for FaceTime (actually it uses the same password for both Messages and FaceTime). Lo and behold FaceTime worked when I entered the new password created by Apple. I then opened Messages and the weird part was that it showed that I was signed in to my account, BUT I was still inactive. I tried using the new password, but that didn't work and got the same "network error" message. Well at least FaceTime works.