I've recently started leading a 25-man pickup group that raids Icecrown Citadel. A few of the DPS classes in my guild are focused on obtaining a Shadowmourne, and so I offered to set up a run so that they can start collecting the legendary shards. While just about everyone has been to a PUG raid, leading them can be quite different from simply participating. The biggest difference for me is deal with the variety of personalities that come together.
Once nice thing about having such a diverse group of people in the raid is it allows me to talk with other healers that I normally wouldn't interact much with. Recently, in our group 5 party chat discussions, the topic of "favorite tank to heal" came up. I had a few particular players in mind, but the healers actually started talking about the tank classes that they preferred to heal. While there's more to tanking than simply picking the right class, the fact is that the tank classes take damage in different ways. Who's your tank of choice when healing?