Do you use RTM? It's always been one of those web apps that seem really useful, but I've never made the leap to actually using it in anger. I suppose you need to adopt it in tandem with the five-point GTD philosophy to get real benefit?
Yes, I do use RTM, and I love it. I've been looking for a decent way of managing my to-do lists effectively for years, and RTM really scratches that itch! I now have the web app permanently open in a Firefox tab, and use "MilkSync" to synchronize with my Pocket PC every half hour.
I'm not sure that you need to adopt a particular task-management philosophy in order to get benefit - RTM is flexible enough to allow you to work the way you want to. I started off pretty basic, with just three lists, one each for personal, business, and current client tasks. But recently (having read that article and re-read the relevant bits of GTD), I have begun using tags and locations and using these to get the benefit of some smart lists. So, I'm currently on the train to work, and I can look at my "@Train" list and see at a glance the stuff tagged with "na" (for "next actions") and a location of @Train - i.e the stuff that I can and should be doing from here!
The RTM website is clean, slick, and easy to use (especially if you make the effort to memorise the keyboard shortcuts), which means there is little friction involved in maintaining your tasks during the day, which of course is vital to making any system work.
One of the other sites that I'm logged into all day long is Gmail, and there's a really good Firefox extension (3.0-compatible) which integrates RTM into Gmail brilliantly - RTM can even automatically create a task when you star a mail.
What else? Did I mention the API, Blackberry support, Offline access (via Google Gears), iGoogle widget, Google Calendar integration, Atom feeds, Twitter integration, Google Maps integration.....? The list goes on - if you can think of a neat feature that you'd like to have in a web app circa 2008, chances are that RTM has it.
Give it a go, but don't blame me if you become dependent upon it!
For the record, I have no connections with Remember The Milk other than being a very happy user of their product. And thanks to Colin for originally bringing RTM to my attention.