SMS is working fine for me on all of my devices. Everything else is very on and off.
Using:
Late 2013 27" iMac
iPad Air
iPhone 5s
iPod touch (5th gen)
All iOS devices were restored as new using iOS 8 beta 1 ipsw. iMac had 10.10 upgraded (not clean installed) from 10.9.3.
Sometimes it works just fine, other times it's like the feature doesn't exist. It works better Mac to iOS, for me. Opening Safari, Mail, etc. on an iOS device, my iMac will only sometimes bring up the Handoff option. Conversely, using a Handoff-enabled app on my iMac almost always brings up the little dimmed icon on the lock screen of my iPad and iPhone (for example, browsing the Maps app on my iMac, I can use it to bring up the same location on my iOS device).
I am willing to bet it has something to do with the interaction of Bluetooth and Wi-Fi. When it works on my iOS device, the Bluetooth icon in the top-right of the device shows it is connected. Occasionally it will look like it's connecting and disconnecting.