Two posts you must read if you care at all about measuring the value of your event:
How Do You Feel About Me? by Judith Lindenau. One quick snip (and thanks to Kevin for the pointer):
The important questions have to do with this question: how applicable was the information you heard to what you do in your job? Or (asked at a later date) “what percentage of the information you gained do you remember? What information from the presentation are you using today?” Certainly retention of information and practical application of methods are important goals for our training efforts. And if we are gauging effectiveness based on those values, conveying those value measurements in advance to course writers and presenters will take your program a long way to success.
The other is the Future of Learning: Get Serious,, in which Lisa Junker at the Acronym blog interviews Jeffrey Cufaude. Along with other topics, he talks about evaluations and how we're basically still stuck at the smiley-face stage. His last line is really staying with me:
My bottom-line takeaway from that is we're not serious about learning. We're serious about delivering information, and that's not sustainable 10 to 20 years from now.