Steve Jobs would use a test audience and ask for feedback in conjunction with lots of practice for his renowned keynotes.

Aimee Mullin's TED talk has gone viral with over 2.3 million views and she explains her final speech was so popular because she was constantly seeking feedback whether it was via Skype or from her seatmate on the plane (source: C. Gallo's Talk like TED)

"Lean In" turned into a book and then a worldwide movement after Sheryl Sandberg delivered her TED talk.  Her original presentation was packed with data when a friend suggested she share the personal story about Sheryl's daughter crying and not wanting her Mom to go to the talk.  (source: C. Gallo's Talk like TED)

The power of feedback is no secret.  Most books on the subject and most professional speakers talk about how feedback tweaked their best presentations in just the right way.  The main challenge is having quick and convenient access to feedback.