Here is the list of feedback compiled from a combination of speaking to participants privately, listening to coffee/tea discussions and Twitter.  Be warned that some of the entries are contradictory, precisely because there is no agreement on some issues.  This list was emailed to Thomas Henning right after Exoplanets II in preparation for Exoplanets III.

Allow prorated registration for parents with kids to attend only part of conference 

Manage balance between number of students versus senior folks wrt early registration 

Improve gender balance of speakers 

Consider mix of main stage versus breakout sessions 

Allow for a long break (~3 hours) in the afternoon 

Consider live video streaming 

Coffee / interaction area needs room with better acoustics 

Clarify embargo policy 

Name on both sides of badge 

Pooled nannies

Deferred payment of registration for NASA employees or individuals in need of aid

Keep structure of session chair (SOC) and assistant session chair (LOC)

Keep free water bottles 

Curated poster sessions each day, where each session is on a coherent theme and introduced in the plenary by a curator (SOC member or senior person) during the main plenary.

Curator picks several posters for 1-minute “elevator pitches”

Printed programs

Avoid splinters / breakout sessions

Longer lunch breaks!

Keep end-of-day drinks to encourage interactions

More snacks during coffee/tea breaks.