How do you judge the success of a conference?

Conferences offer a diversity of opportunities. I can't remember the last time I left one without a lot to feel positive about. Does that mean each one was a success as is invariably claimed by the organizers? What does success mean? Have you ever been to a conference which excelled in every dimension?

Perhaps the event was successful for me as an attendee, but what about the others involved ... exhibitors, speakers, organizers, sponsors, volunteers ... even facilities staff?

Was registration efficient with no long queues, material ready and as ordered?
Not overcrowded, or undercrowded?

Could you see the slides ... screen large enough, adequate contrast and size to be readable, adequate sight lines?
Could you understand the speaker ... audio technology worked, external noise, the speaker was clear and was comprehensible (accent!)?
Was the room comfortable ... temperature, seating, under or over-crowded?
Was there a session chair who took pains to ensure the speaker was as comfortable as possible (water, A/V working), briefly introduce and thank the speaker, make brief administrative announcements, handle unexpected distractions?

Was there reliable wifi?

Was the marketplace area located so that exhibitors could get adequate traffic? 

AND as anyone who has reviewed the post-conference survey forms appreciates ... refreshments?