Three observations:
1) He really is good on his feet with concise answers - and a willingness to be open that everything is not firm yet.
2) Some Republicans just want to filibuster -- and JK was funny when the Chair indicated that if the members used all the time, Kerry would have to respond in writing. He smiled and said he had no problem with just sitting listening to questions. Many Rs were simply rude - especially one (from Texas) who thought he was clever in rambling on asking who the enemy was, who was attacked and the plan. ( This had to do with the Republican mantra that the fight was against radical Islam. Kerry's answer was great - that SOME were motivated by a distorted version of Islam, but many were criminal thugs .. adventurers.
3) Kerry's good nature, politeness and patience was pretty unbelievable.
Many Democrats were great - Meeks listed many examples of leadership of multinational efforts as what he said were examples of real leadership. Another Democrat listed many things including eliminating the Syrian chemical weapons that could otherwise have potentially been in ISIS hands in a long list of things that he credited Obama/Kerry for.
A very neat answer was given when asked to respond to Netanyahu's comments - Kerry noted that just as he was asking people to wait until they saw what was in the plan before attacking it, he should wait to hear Netanyahu's speech -- and that he would respond if he disagreed. Very nice indirect slap as he took the high road.