Need LR4 workflow advice for large event photography, RAW vs. JPG

I want to second Photo Chris' recommendation for Martin Evening's book on Lightroom 4. I was lost with Lightroom until I went through his earlier book on LR2. I stopped shooting jpegs as soon as I understood how easy it is to work with raw files in Lightroom. I've gotten Martin Evening's books on LR3 and LR4 as they've been released. I also think each new version of LR has been well worth the cost of upgrading.

Oh yes, I convert to dng when I import.  If you're shooting jpegs I would leave them as jpegs.  You shouldn't ever modify the original file when you use Lightroom.

John