Mainly those I develop myself - SDWF and Stewart's Utility Library.
I hope so.
No.
Yes, though I'm not sure that libraries and IDE support are quite ready yet. And D isn't quite ready for significant third-party implementation, which might play a part in reaching this stage.
I do most of my editing in TextPad. Which admittedly isn't fully compatible with D (two missing syntax highlighting features, and doesn't support Unicode), but it works.