Sujee Maniyam gave an excellent presentation on "Cost Effective Big-Data Processing using Amazon Elastic Map Reduce". Here is the link to the slides, http://www.slideshare.net/sujee/cost-effective-bigdata-processing-on-amazon-ec2
The remote format worked out great: we could join people from other places, using Skype and joinme.com. The speakers made everybody in the room hear, and we could ask Sujee questions that he could hear and answer. The slides were projected on the wall (thanks to Alan Lipe), and the fun was had by all.
The gist of it is that Amazon is great for quick prototyping, and EMR - even more so, if you can make it work for you. But in the long run, it can get pretty expensive (as was evidenced by me last week, when I left a 6-machine cluster running for week, 192 hours).
Thank you all!