I love this idea. Great suggestion @AndyW 

Obviously they're not as powerful (or character-unlimited) as listVars, but I do want to remind this group that listprops can still be extremely powerful too. You'll be able to mix and match events to listprop values, plus Classifications can be applied to them too!

I'd say it'd be super helpful for IP-based processing rules (a la http://ideas.omniture.com/t5/Idea-Exchange-for-Adobe/Add-Regular-Expression-type-feature-t o-Processing-Rules/idi-p/5067). The current string-based Processing Rule options make it very difficult to deal with IP ranges.