Photoshop Seminar

So, I went to an Adobe 'What's new in Photoshop' seminar yesterday at the Fine Arts Building in downtown Chicago. First of all, that building is just amazing! The architecture is so beautiful, you've really got to see it to believe it. Check it out here:http://www.fineartsbuilding.tv/
Anyway, the seminar had about 10 people there of varying knowledge of Photoshop, some of us were very experienced with it, some not so much. I won't say that it was a waste of time, I did learn something new, the 'content fill' tool. Might just give that a shot.
But, I didn't care for how the instructor was working directly on the original background layer by just renaming it 'layer 0'. What if you need to go back to the original? I guess I've just learned to do as little destructive work as possible.
So let me know if you've been to any workshops, seminars, classes etc on Photoshop. What did you get out of it? What would like to see improved? How would you teach the class?