I've been gtd'ing for a year, and email was always the weakest link. My action lists were alright, but my email folders (@Action, @WaitingFor) were this black hole that I would dread looking in, and in fact wouldn't look in until the weekly review (er, make that two-week review).
Anyway, the GTD Outlook Plugin seems to be helping me a lot. Because it converts the actionable emails into tasks, the email-related actions are in my face rather than stuffed out of sight into email folders. The actions are now in my Task lists, which I look at often.
It's $70, but it's enough of an improvement to my life that I'm going to bite the bullet.