How well does GMail let me create filters to handle heavy traffic lists?
GMail is not perfect, but it's got the workflow down right. When I want to add a filter, I am probably looking at a message that I want the filter to match. So GMail's "Filter messages like this" command is a great match. They also know about lists, and they auto-populate the search command for the filter with the "list:email@example.com" style search. This works out pretty great, and I've been using GMail for lists for years.
It works to divert the flood out of my inbox, but it can also mean that for lists that aren't related to my job, I have basically unsubscribed to the list - out of sight, out of mind. I sometimes add filters to automatically "star" conversations I'm likely to want to look at, but that's not the best choice - it overloads the meaning of the star, and I'd rather see either tags that aren't full labels (and don't clutter up my label list) or a some other flag-like bit that is only set by filters to say when something might be interesting.