Surely debugging support on platforms other than linux is much more important than any of these things you have listed. These things may be nice, but absolutely unnecessary. Integrated debugging is a must.
Personally I don't want to waste time with scanning tons of API documentation just to find out what parameters my called phobos function has got. In larger projects, with large amounts of classes and methods it'll be hard to find everything in a short time.
So I doubt that code completion is that unnecessary.
Debugging is important, for sure, but without having abstract access to the debugged code it'll be quite impossible to e.g. read out memory and to know what this memory represents. Just imagine I was given a pointer address but don't know that it's a string[]? And now imagine you want to debug mixed-in code? I guess you won't be able to do this without knowing what your mixin code finally looks like :)
