I think 8.2 might have broken Do Not Disturb (per conversation) for me.
On one of my iPhone 6 Plus', I have all messages threads turned to DND in the Details section of the message thread (device-wide DND is not enabled). Before applying 8.2, my screen would light up, but the device would not vibrate or make a sound when I got an incoming message. Now, it acts as if I don't have DND on at all. Vibrates and makes the incoming message sound that I have set.
Deleted all conversation and restarted them, did the usual steps even all the way through restoring and setting up as new. Still vibrating and making notification sounds when I get a message.
Gonna see if the same thing happens on any of my development iPads as well shortly here, and will update. In the meantime, can anybody confirm that DND per-conversation IS or IS NOT working for them?
EDIT: It randomly started working. I updated my iPad Air 2 to 8.2 beta (which may or may not be related), and now suddenly DND per-conversation is working on both. In fact, now, instead of the screen lighting up and the message showing up on the lock screen even though DND is on, the screen stays off and the conversation that has DND engaged does not show notifications on the lock screen. That's better than before!