I still use RTM fwiw. I try new todo/task managers quite often, but always end up back at remember the milk. My only complaint about it is that it's not opensource so I can't self-host it.

I'm currently trying out SilverBullet.md as a markdown note tool and task management. The UX isn't close to rtm, but it's pretty customizable so I'm hoping I can make it close.

I never used Remember the Milk but FWIW you can assign numbered keyboard shortcuts for labels and make smart lists with those labels, so I think you could recreate that flow with Godspeed!

Remember the Milk is still around and one of the best pieces of software I've ever used! Plus - it's not Mac-exclusive.