Great thread, everyone!
For those who heat their first runnings right away: any concerns/experiences with caramelization due to heating such a small volume?
I have not had any problems at all, even with some of my light lagers. One of my regular recipes calls for first wort hopping and suggests keeping the run off at about 170F until it is finished, then to ramp up for the boil as usual. I never bring it to a boil until the sparge is finished, although with non FWH beers I go ahead and heat it towards boiling as I am sparging. No excessive caramelizing either way that I can detect. I say excessive as I am sure there is some darkening of the wort when boiling no matter what. I think some degree of caramelization is unavoidable and even desirable in many styles.