I was using the related_tweets endpoint in V1, and when it was depreciated in V1.1, this caused big problems for the application I was working on.
I had to create a workaround, which I have documented here, http://adriancrepaz.com/twitter_conversations_api
It scrapes Twitter and it’s very reliable.
I’ve used it for the past few months and have successfully returned thousands of conversations.
If Twitter change their markup, I’ll update the code on Github.
Hope it helps,
Adrian