I don't know. I often note down key points on my phone anyway, just in my notes. The times I've live tweeted, I just decided to share the note instead. I like being able to look back at the end of the day and see the key points from that session. I think I remember it much better with that memory hook. A full day of conference sessions and meeting people in between can become a blur after.

I don't read tweets while in session, but it might be a good idea to check for DMs or something, to see if a coworker or peer wants me to ask something during the Q&A. All the Google IO sessions may be on YouTube nowadays, but you still have the best chance to get your question answered if you are there live or have a proxy.