FBX Export could do with being improved significantly. This is the only thing I use DS for.

I too like the idea of Left and Right feet cameras. Whilst we are talking about cameras, I'd prefer a grid of camera icons instead of having to use drop-downs or clicking the "Select Camera" icon multiple times. Even better if we could in preferences choose which camera icons were shown.

I too would love decent rulers and guides, for years I've had to use simple cuboid models as in-scene guides to aid precise placement when creating animations.