but yeah, i don't particularly like silverlight myself. it's kinda SUVvy for me, indeed.
Silverlight is competing in its own category. Its doing itself no favors by making mistakes like this.
It's about baseline. If trying to compete, first you absolutely need all expected functionality. At that point, your product is worth exactly zero. It's a commodity. Features that come on top of that are what adds value.
When it comes to details like this, Microsoft went downhill during Vista and 7 era. Windows Explorer is a usability disaster, I've started preferring command prompt. And Windows is very far from an OS that could afford to hide the file system.
But a better question for the problem at hand - why is there a need for Save As dialog? Why isn't the application presenting user's cloud-/intra-/VPN-based repository via commonly accepted and standard web interface? Why does application expose something so quaint and arcane as Files and File system?
This was the major issue I was trying to expose. World has moved beyond files, yet many developers will be forced to deal with patching around WPF Latest.Greatest.4.5.Enterprise.Beta technology stack.