The best D IDE will not be complete without the following features...
(make sure to add enough detail for those of us who have not seen your feature elsewhere to get what you mean)
- Linux support (there isn't a single good D IDE for Linux - but several for Windows like D-IDE? and Poseidon)
- Support for D1 and D2
- Typing words and stuff...
- Syntax Highlighting (Make comments, keywords, and other language tokens different colors)
- Code completion (Hit tab to fill in that extra long identifier; list possible class methods,data.)
- Code completion (Hit <ctl>+<tab> to fill in the rest of your method with the obvious solution.)
- Comment/uncomment line/selection with a shortcut (that's why I still sit on Kate, ctrl-d to comment, shift-ctrl-d to uncomment)
- Refactoring, e.g. rename a method/class/field/module/package/... and the whole workspace is updated accordingly and no more search-and-replace by hand is necessary. Also support for moving a class to another module or a module to another package etc would be nice. Eclipse's refactoring support for Java might be a good source of inspiration.
- Show (formatted) Doc comments on autocompletion and when clicking on a word or something (again, Eclipses Java/javadoc support might be a good inspiration)
- Generate basic Doc comments for Methods (parameters, return type might be prepared)
- Function call graph
- Calling some external command to build project (like make, rebuild etc) - and parse output to highlight compiler errors in the editor accordingly
- Jump to line numbers output by GDB
- Integrated debugging (with GDB or DDbg as appropriate) -- set breakpoints, inspect symbols
- Support for revision control (like SVN, git, hg, ..) - at least basic support ("add file to revision control", "commit current changes", "update from repository") would be nice.