ListSource Output Fields - What do you use?

[Matt Pastier]

Hey everyone - 

I'm working on putting together my first mailing lists using ListSource. I narrowed it down to my major strategy/criteria. Before purchasing it's giving me the option of adding additional output fields. Some make sense to me to add because it'll make my work faster. Others I'm not sure. 

Do you have any outputs you use that are worth the extra money because they help you in some way?